Patent Publication Number: US-6702710-B1

Title: Multi-speed planetary transmissions with a stationary interconnection

Description:
TECHNICAL FIELD 
     The present invention relates to a family of power transmissions having three planetary gear sets that are controlled by six torque-transmitting devices to provide at least seven forward speed ratios and one reverse speed ratio. 
     BACKGROUND OF THE INVENTION 
     Passenger vehicles include a powertrain that is comprised of an engine, multi-speed transmission, and a differential or final drive. The multi-speed transmission increases the overall operating range of the vehicle by permitting the engine to operate through its torque range a number of times. The number of forward speed ratios that are available in the transmission determines the number of times the engine torque range is repeated. Early automatic transmissions had two speed ranges. This severely limited the overall speed range of the vehicle and therefore required a relatively large engine that could produce a wide speed and torque range. This resulted in the engine operating at a specific fuel consumption point during cruising, other than the most efficient point. Therefore, manually-shifted (countershaft transmissions) were the most popular. 
     With the advent of three- and four-speed automatic transmissions, the automatic shifting (planetary gear) transmission increased in popularity with the motoring public. These transmissions improved the operating performance and fuel economy of the vehicle. The increased number of speed ratios reduces the step size between ratios and therefore improves the shift quality of the transmission by making the ratio interchanges substantially imperceptible to the operator under normal vehicle acceleration. 
     It has been suggested that the number of forward speed ratios be increased to six or more. Six-speed transmissions are disclosed in U.S. Pat. No. 4,070,927 issued to Polak on Jan. 31, 1978; U.S. Pat. No. 6,071,208 issued to Koivunen on Jun. 6, 2000; U.S. Pat. No. 5,106,352 issued to Lepelletier on Apr. 21, 1992; and U.S. Pat. No. 5,599,251 issued to Beim and McCarrick on Feb. 4, 1997. 
     Six-speed transmissions offer several advantages over four- and five-speed transmissions, including improved vehicle acceleration and improved fuel economy. While many trucks employ power transmissions having six or more forward speed ratios, passenger cars are still manufactured with three- and four-speed automatic transmissions and relatively few five or six-speed devices due to the size and complexity of these transmissions. The Polak transmission provides six forward speed ratios with three planetary gear sets, two clutches, and three brakes. The Koivunen and Beim patents utilize six torque-transmitting devices including four brakes and two clutches to establish six forward speed ratios and a reverse ratio. The Lepelletier patent employs three planetary gear sets, three clutches and two brakes to provide six forward speeds. One of the planetary gear sets is positioned and operated to establish two fixed speed input members for the remaining two planetary gear sets. Seven-speed transmissions are disclosed in U.S. Pat. Nos. 4,709,594 to Maeda; U.S. Pat. No. 6,053,839 to Baldwin et. al.; and U.S. Pat. No. 6,083,135 to Baldwin et. al. Seven- and eight-speed transmissions provide further improvements in acceleration and fuel economy over six-speed transmissions. However, like the six-speed transmissions discussed above, the development of seven- and eight-speed transmissions has been precluded because of complexity, size and cost. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved family of transmissions having three planetary gear sets controlled to provide at least seven forward speed ratios and one reverse speed ratio. 
     In one aspect of the present invention, the family of transmissions has three planetary gear sets, each of which includes a first, second and third member, which members may comprise a sun gear, a ring gear, or a planet carrier assembly member. 
     In referring to the first, second and third gear sets in this description and in the claims, these sets may be counted “first” to “third” in any order in the drawings (i.e., left to right, right to left, etc.). 
     In another aspect of the present invention, each of the planetary gear sets may be of the single pinion-type or of the double pinion-type. 
     In yet another aspect of the present invention, the first member of the first planetary gear set is continuously interconnected with the first member of the second planetary gear set and a stationary member (transmission housing) through a first interconnecting member. 
     In yet another aspect of the present invention, the second member of the second planetary gear set is continuously interconnected with the first member of the third planetary gear set through a second interconnecting member. 
     In yet a further aspect of the invention, each family member incorporates an input shaft which is continuously connected with a member of the planetary gear sets and an output shaft which is continuously connected with another member of the planetary gear sets. 
     In still a further aspect of the invention, a first torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first planetary gear set with the input shaft, output shaft or a member of the second or third planetary gear set. 
     In another aspect of the invention, a second torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the second planetary gear set with the input shaft, output shaft or a member of the first or third planetary gear set. 
     In a still further aspect of the invention, a third torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the third planetary gear set with the input shaft, the output shaft, or a member of the first or second planetary gear set. 
     In a still further aspect of the invention, a fourth torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first or second planetary gear set or the second interconnecting member with another member of the first, second or third planetary gear set. 
     In a still further aspect of the invention, a fifth torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the second or third planetary gear set or the second interconnecting member with another member of the first, second or third planetary gear set. 
     In still another aspect of the invention, a sixth torque-transmitting mechanism, such as a clutch, selectively interconnects a member of the first, second or third planetary gear set with another member of the first, second or third planetary gear set. Alternatively, the sixth torque-transmitting mechanism, such as a brake, selectively connects a member of the first, second or third planetary gear set with the stationary member (transmission case). 
     In still another aspect of the invention, the six torque-transmitting mechanisms are selectively engageable in combinations of two to yield at least seven forward speed ratios and one reverse speed ratio. 
    
    
     The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a schematic representation of a powertrain including a planetary transmission incorporating a family member of the present invention; 
     FIG. 1 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 1 a;    
     FIG. 2 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 2 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 2 a;    
     FIG. 3 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 3 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 3 a;    
     FIG. 4 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 4 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 4 a;    
     FIG. 5 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 5 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 5 a;    
     FIG. 6 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 6 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 6 a;    
     FIG. 7 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; 
     FIG. 7 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 7 a;    
     FIG. 8 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; and 
     FIG. 8 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 8 a.   
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like characters represent the same or corresponding parts throughout the several views, there is shown in FIG. 1 a  a powertrain  10  having a conventional engine and torque converter  12 , a planetary transmission  14 , and a conventional final drive mechanism  16 . 
     The planetary transmission  14  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  18 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  18  includes three planetary gear sets  20 ,  30  and  40 . 
     The planetary gear set  20  includes a sun gear member  22 , a ring gear member  24 , and a planet carrier assembly  26 . The planet carrier assembly  26  includes a plurality of pinion gears  27  rotatably mounted on a carrier member  29  and disposed in meshing relationship with both the sun gear member  22  and the ring gear member  24 . 
     The planetary gear set  30  includes a sun gear member  32 , a ring gear member  34 , and a planet carrier assembly member  36 . The planet carrier assembly member  36  includes a plurality of pinion gears  37  rotatably mounted on a carrier member  39  and disposed in meshing relationship with both the sun gear member  32  and the ring gear member  34 . 
     The planetary gear set  40  includes a sun gear member  42 , a ring gear member  44 , and a planet carrier assembly member  46 . The planet carrier assembly member  46  includes a plurality of pinion gears  47  rotatably mounted on a carrier member  49  and disposed in meshing relationship with both the sun gear member  42  and the ring gear member  44 . 
     The planetary gear arrangement also includes six torque-transmitting mechanisms  50 ,  52 ,  54 ,  56 ,  58  and  59 , each of which is a rotating-type torque-transmitting mechanism, commonly termed clutch. 
     The input shaft  17  is continuously connected with the sun gear member  22 , and the output shaft  19  is continuously connected with the ring gear member  44 . The ring gear member  24  is continuously connected with the ring gear member  34  and the transmission housing  60  through the interconnecting member  70 . The sun gear member  32  is continuously connected with the sun gear member  42  through the interconnecting member  72 . 
     The sun gear member  22  is selectively connectable with the sun gear member  32  through the clutch  50 . The sun gear member  22  is selectively connectable with the planet carrier assembly member  46  through the clutch  52 . The planet carrier assembly member  26  is selectively connectable with the sun gear member  32  through the clutch  54 . The planet carrier assembly member  26  is selectively connectable with the planet carrier assembly member  36  through the clutch  56 . The planet carrier assembly member  36  is selectively connectable with the planet carrier assembly member  46  through the clutch  58 . The planet carrier assembly member  36  is selectively connectable with the ring gear member  44  through the clutch  59 . 
     As shown in FIG. 1 b , and in particular the truth table disclosed therein, the torque-transmitting mechanisms are selectively engaged in combinations of two to provide seven forward speed ratios and a reverse speed ratio. 
     The reverse speed ratio is established with the engagement of the clutches  56  and  58 . The clutch  56  connects the planet carrier assembly members  26  and  36 . The clutch  58  connects the planet carrier assembly members  36  and  46 . The sun gear member  22  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  26 ,  36  and  46  rotate at the same speed. The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  26  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The sun gear members  32 ,  42  rotate at the same speed. The sun gear member  32  rotates at a speed determined from the speed of the planet carrier assembly member  36  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30  and  40 . 
     The first forward speed ratio is established with the engagement of the clutches  54  and  59 . The clutch  54  connects the planet carrier assembly member  26  to the sun gear member  32 . The clutch  59  connects the planet carrier assembly member  36  to the ring gear member  44 . The sun gear member  22  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  26  and the sun gear members  32 ,  42  rotate at the same speed. The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  26  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The planet carrier assembly member  36  and the ring gear member  44  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  36 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20  and  30 . 
     The second forward speed ratio is established with the engagement of the clutches  50  and  59 . The clutch  50  connects the sun gear member  22  to the sun gear member  32 . The clutch  59  connects the planet carrier assembly member  36  to the ring gear member  44 . The sun gear members  22 ,  32  and  42  rotate at the same speed as the input shaft  17 . The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  36  and the ring gear member  44  rotate at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  42 , the speed of the planet carrier assembly member  46  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  30 . 
     The third forward speed ratio is established with the engagement of the clutches  56  and  59 . The clutch  56  connects the planet carrier assembly member  26  to the planet carrier assembly member  36 . The clutch  59  connects the planet carrier assembly member  36  to the ring gear member  44 . The sun gear member  22  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  26 ,  36  and the ring gear member  44  rotate at the same speed as the output shaft  19 . The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  26 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The sun gear members  32 ,  42  rotate at the same speed. The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  20 . 
     The fourth forward speed ratio is established with the engagement of the clutches  52  and  59 . The clutch  52  connects the sun gear member  22  to the planet carrier assembly member  46 . The clutch  59  connects the planet carrier assembly member  36  to the ring gear member  44 . The sun gear member  22  and the planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  36  and the ring gear member  44  rotate at the same speed as the output shaft  19 . The sun gear members  32 ,  42  rotate at the same speed. The planet carrier assembly member  36  rotates at a speed determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  30  and  40 . 
     The fifth forward speed ratio is established with the engagement of the clutches  52  and  56 . The clutch  52  connects the sun gear member  22  to the planet carrier assembly member  46 . The clutch  56  connects the planet carrier assembly member  26  to the planet carrier assembly member  36 . The sun gear member  22  and the planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The planet carrier assembly members  26 ,  36  rotate at the same speed. The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  26  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The sun gear members  32 ,  42  rotate at the same speed. The planet carrier assembly member  36  rotates at a speed determined from the speed of the sun gear member  32  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30  and  40 . 
     The sixth forward speed ratio is established with the engagement of the clutches  50  and  52 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the sixth forward speed ratio is 1. 
     The seventh forward speed ratio is established with the engagement of the clutches  52  and  54 . The clutch  52  connects the sun gear member  22  to the planet carrier assembly member  46 . The clutch  54  connects the planet carrier assembly member  26  to the sun gear member  32 . The sun gear member  22  and the planet carrier assembly member  46  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  26  rotates at the same speed as the sun gear members  32  and  42 . The ring gear members  24 ,  34  do not rotate. The planet carrier assembly member  26  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The ring gear member  44  rotates at the same speed as the output shaft  19 . The ring gear member  44 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  46 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The numerical value of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20  and  40 . 
     As set forth above, the engagement schedule for the torque-transmitting mechanisms is shown in the truth table of FIG. 1 b . This truth table also provides an example of speed ratios that are available utilizing the ring gear/sun gear tooth ratios given by way of example in FIG. 1 b . The R 1 /S 1  value is the tooth ratio of the planetary gear set  20 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  30 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  40 . Also, the chart of FIG. 1 b  describes the ratio steps that are attained utilizing the sample of tooth ratios given. For example, the step ratio between the first and second forward speed ratios is 2.50, while the step ratio between the reverse and first forward ratio is −1.40. It can also be readily determined from the truth table of FIG. 1 b  that all of the single step forward ratio interchanges are of the single transition variety, except the reverse to first step. The double step forward interchanges are of the single transition variety as well. 
     FIG. 2 a  shows a powertrain  110  having a conventional engine and torque converter  12 , a planetary transmission  114 , and a conventional final drive mechanism  16 . 
     The planetary transmission  114  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  118 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  118  includes three planetary gear sets  120 ,  130  and  140 . 
     The planetary gear set  120  includes a sun gear member  122 , a ring gear member  124 , and a planet carrier assembly  126 . The planet carrier assembly  126  includes a plurality of pinion gears  127  rotatably mounted on a carrier member  129  and disposed in meshing relationship with both the sun gear member  122  and the ring gear member  124 . 
     The planetary gear set  130  includes a sun gear member  132 , a ring gear member  134 , and a planet carrier assembly member  136 . The planet carrier assembly member  136  includes a plurality of pinion gears  137  rotatably mounted on a carrier member  139  and disposed in meshing relationship with both the sun gear member  132  and the ring gear member  134 . 
     The planetary gear set  140  includes a sun gear member  142 , a ring gear member  144 , and a planet carrier assembly member  146 . The planet carrier assembly member  146  includes a plurality of pinion gears  147  rotatably mounted on a carrier member  149  and disposed in meshing relationship with both the sun gear member  142  and the ring gear member  144 . 
     The planetary gear arrangement  118  also includes six torque-transmitting mechanisms  150 ,  152 ,  154 ,  156 ,  158  and  159 . The torque-transmitting mechanisms  150 ,  152 ,  154 ,  156  and  158  are rotating-type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanism  159  is a stationary-type torque transmitting mechanism, commonly termed brake or reaction clutch. 
     The input shaft  17  is continuously connected with the ring gear member  124 , and the output shaft  19  is continuously connected with the ring gear member  144 . The sun gear member  122  is continuously connected with the ring gear member  134  and the transmission housing  160  through the interconnecting member  170 . The sun gear member  132  is continuously connected with the planet carrier assembly member  146  through the interconnecting member  172 . 
     The ring gear member  124  is selectively connectable with the sun gear member  142  through the clutch  150 . The planet carrier assembly member  126  is selectively connectable with the sun gear member  132  through the clutch  152 . The planet carrier assembly member  126  is selectively connectable with the planet carrier assembly member  136  through the clutch  154 . The planet carrier assembly member  136  is selectively connectable with the ring gear member  144  through the clutch  156 . The ring gear member  144  is selectively connectable with the sun gear member  142  through the clutch  158 . The planet carrier assembly member  136  is selectively connectable with the transmission housing  160  through the brake  159 . 
     The truth table of FIG. 2 b  describes the engagement sequence utilized to provide seven forward speed ratios and a reverse speed ratio in the planetary gear arrangement  118  shown in FIG. 2 a.    
     The reverse speed ratio is established with the engagement of the clutch  150  and the brake  159 . The clutch  150  connects the ring gear member  124  to the sun gear member  142 . The brake  159  connects the planet carrier assembly member  136  to the transmission housing  160 . The ring gear member  124  and the sun gear member  142  rotate at the same speed as the input shaft  17 . The sun gear member  122 , the planetary gear set  130  and the planet carrier assembly member  146  do not rotate. The ring gear member  144  rotates at the same speed as the output shaft  19 . The ring gear member  144 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  140 . 
     The first forward speed ratio is established with the engagement of the clutches  150  and  156 . The clutch  150  connects the ring gear member  124  to the sun gear member  142 . The clutch  156  connects the planet carrier assembly member  136  to the ring gear member  144 . The ring gear member  124  and the sun gear member  142  rotate at the same speed as the input shaft  17 . The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  136  and the ring gear member  144  rotate at the same speed as the output shaft  19 . The sun gear member  132  and the planet carrier assembly member  146  rotate at the same speed. The planet carrier assembly member  136  rotates at a speed determined from the speed of the sun gear member  132  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The ring gear member  144 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  146 , the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  130  and  140 . 
     The second forward speed ratio is established with the engagement of the clutches  152  and  156 . The clutch  152  connects the sun gear member  132  to the planet carrier assembly member  126 . The clutch  156  connects the planet carrier assembly member  136  to the ring gear member  144 . The ring gear member  124  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  126  and  146  rotate at the same speed as the sun gear member  132 . The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the ring gear member  124  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The planet carrier assembly member  136  and the ring gear member  144  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  136 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  132  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120  and  130 . 
     The third forward speed ratio is established with the engagement of the clutches  150  and  152 . The clutch  150  connects the ring gear member  124  to the sun gear member  142 . The clutch  152  connects the planet carrier assembly member  126  to the sun gear member  132 . The ring gear member  124  and the sun gear member  142  rotate at the same speed as the input shaft  17 . The planet carrier assembly members  126  and  146  rotate at the same speed as the sun gear member  132 . The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the ring gear member  124  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The ring gear member  144  rotates at the same speed as the output shaft  19 . The ring gear member  144 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  146 , the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120  and  140 . 
     The fourth forward speed ratio is established with the engagement of the clutches  152  and  158 . The clutch  152  connects the planet carrier assembly member  26  to the sun gear member  132 . The clutch  158  connects the ring gear member  144  to the sun gear member  142 . The ring gear member  124  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  126 , the sun gear member  132  and the planetary gear set  140  rotate at the same speed as the output shaft  19 . The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  126 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  124  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  120 . 
     The fifth forward speed ratio is established with the engagement of the clutches  150  and  158 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the fifth forward speed ratio is 1. 
     The sixth forward speed ratio is established with the engagement of the clutches  154  and  158 . The clutch  154  connects the planet carrier assembly member  126  to the planet carrier assembly member  136 . The clutch  158  connects the ring gear member  144  to the sun gear member  142 . The ring gear member  124  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  126  and  136  rotate at the same speed. The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the ring gear member  124  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The sun gear member  132  and the planetary gear set  140  rotate at the same speed as the output shaft  19 . The sun gear member  132 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  136  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The numerical value of the sixth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120  and  130 . 
     The seventh forward speed ratio is established with the engagement of the clutches  150  and  154 . The clutch  150  connects the ring gear member  124  to the sun gear member  142 . The clutch  154  connects the planet carrier assembly member  126  to the planet carrier assembly member  136 . The ring gear member  124  and the sun gear member  142  rotate at the same speed as the input shaft  17 . The planet carrier assembly members  126  and  136  rotate at the same speed. The sun gear member  122  and the ring gear member  134  do not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the ring gear member  124  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The sun gear member  132  rotates at the same speed as the planet carrier assembly member  146 . The planet carrier assembly member  136  rotates at a speed determined from the speed of the sun gear member  132  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The ring gear member  144  rotates at the same speed as the output shaft  19 . The ring gear member  144 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  146 , the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The numerical value of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120 ,  130  and  140 . 
     As set forth above, the truth table of FIG. 2 b  describes the engagement sequence of the torque-transmitting mechanisms utilized to provide a reverse drive ratio and seven forward speed ratios. The truth table also provides an example of the ratios that can be attained with the family members shown in FIG. 2 a  utilizing the sample tooth ratios given in FIG. 2 b . The R 1 /S 1  value is the tooth ratio of the planetary gear set  120 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  130 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  140 . Also shown in FIG. 2 b  are the ratio steps between single step ratios in the forward direction as well as the reverse to first ratio step ratio. For example, the first to second step ratio is 1.54. 
     Turning to FIG. 3 a , a powertrain  210  includes the engine and torque converter  12 , a planetary transmission  214 , and a final drive mechanism  16 . The planetary transmission  214  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  218 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  218  includes three planetary gear sets  220 ,  230  and  240 . 
     The planetary gear set  220  includes a sun gear member  222 , a ring gear member  224 , and a planet carrier assembly  226 . The planet carrier assembly  226  includes a plurality of pinion gears  227  rotatably mounted on a carrier member  229  and disposed in meshing relationship with both the sun gear member  222  and the ring gear member  224 . 
     The planetary gear set  230  includes a sun gear member  232 , a ring gear member  234 , and a planet carrier assembly member  236 . The planet carrier assembly member  236  includes a plurality of pinion gears  237  rotatably mounted on a carrier member  239  and disposed in meshing relationship with both the sun gear member  232  and the ring gear member  234 . 
     The planetary gear set  240  includes a sun gear member  242 , a ring gear member  244 , and a planet carrier assembly member  246 . The planet carrier assembly member  246  includes a plurality of pinion gears  247  rotatably mounted on a carrier member  249  and disposed in meshing relationship with both the sun gear member  242  and the ring gear member  244 . 
     The planetary gear arrangement  218  also includes six torque-transmitting mechanisms  250 ,  252 ,  254 ,  256 ,  258  and  259 . The torque-transmitting mechanisms  250 ,  252 ,  254 ,  256 ,  258  and  259  are rotating type torque-transmitting mechanisms, commonly termed clutches. 
     The input shaft  17  is continuously connected with the ring gear member  224 , and the output shaft  19  is continuously connected with the ring gear member  244 . The sun gear member  222  is continuously connected with the ring gear member  234  and the transmission housing  260  through the interconnecting member  270 . The sun gear member  232  is continuously connected with the planet carrier assembly member  246  through the interconnecting member  272 . 
     The ring gear member  224  is selectively connectable with the sun gear member  242  through the clutch  250 . The planet carrier assembly member  226  is selectively connectable with the sun gear member  232  through the clutch  252 . The planet carrier assembly member  226  is selectively connectable with the planet carrier assembly member  236  through the clutch  254 . The planet carrier assembly member  236  is selectively connectable with the sun gear member  232  through the clutch  256 . The ring gear member  244  is selectively connectable with the planet carrier assembly member  246  through the clutch  258 . The planet carrier assembly member  236  is selectively connectable with the ring gear member  244  through the clutch  259 . 
     As shown in the truth table in FIG. 3 b , the torque-transmitting mechanisms are engaged in combinations of two to establish seven forward speed ratios and one reverse ratio. 
     The reverse speed ratio is established with the engagement of the clutches  250  and  256 . The clutch  250  connects the ring gear member  224  to the sun gear member  242 . The clutch  256  connects the planet carrier assembly member  236  to the sun gear member  232 . The ring gear member  224  and the sun gear member  242  rotate at the same speed as the input shaft  17 . The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly members  236 ,  246  rotate at the same speed as the sun gear member  232 . The ring gear member  244  rotates at the same speed as the output shaft  19 . The ring gear member  244 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  246 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  240 . 
     The first forward speed ratio is established with the engagement of the clutches  250  and  259 . The clutch  250  connects the ring gear member  224  to the sun gear member  242 . The clutch  259  connects the planet carrier assembly member  236  to the ring gear member  244 . The ring gear member  224  and the sun gear member  242  rotate at the same speed as the input shaft  17 . The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  236  and the ring gear member  244  rotate at the same speed as the output shaft  19 . The sun gear member  232  rotates at the same speed as the planet carrier assembly member  236 . The planet carrier assembly member  236  rotates at a speed determined from the speed of the sun gear member  232  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The ring gear member  244 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  246 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  230  and  240 . 
     The second forward speed ratio is established with the engagement of the clutches  252  and  259 . The clutch  252  connects the planet carrier assembly member  226  to the sun gear member  232 . The clutch  259  connects the planet carrier assembly member  236  to the ring gear member  244 . The ring gear member  224  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  226 ,  246  and the sun gear member  232  rotate at the same speed. The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  226  rotates at a speed determined from the speed of the ring gear member  224  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The planet carrier assembly member  236  and the ring gear member  244  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  236 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  232  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220  and  230 . 
     The third forward speed ratio is established with the engagement of the clutches  250  and  252 . The clutch  250  connects the ring gear member  224  to the sun gear member  242 . The clutch  252  connects the planet carrier assembly member  226  to the sun gear member  232 . The ring gear member  224  and the sun gear member  242  rotate at the same speed as the input shaft  17 . The planet carrier assembly members  226 ,  246  rotate at the same speed as the sun gear member  232 . The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  226  rotates at a speed determined from the speed of the ring gear member  224  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The ring gear member  244  rotates at the same speed as the output shaft  19 . The ring gear member  244 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  246 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220  and  240 . 
     The fourth forward speed ratio is established with the engagement of the clutches  252  and  258 . The clutch  252  connects the planet carrier assembly member  226  to the sun gear member  232 . The clutch  258  connects the ring gear member  244  to the planet carrier assembly member  246 . The ring gear member  224  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  226 , the sun gear member  232 , and the planetary gear set  240  rotate at the same speed as the output shaft  19 . The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  226 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  224  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  220 . 
     The fifth forward speed ratio is established with the engagement of the clutches  250  and  258 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the fifth forward speed ratio is 1. 
     The sixth forward speed ratio is established with the engagement of the clutches  254  and  258 . The clutch  254  connects the planet carrier assembly member  226  to the planet carrier assembly member  236 . The clutch  258  connects the ring gear member  244  to the planet carrier assembly member  246 . The ring gear member  224  rotates at the same speed as the input shaft  17 . The planet carrier assembly members  226 ,  236  rotate at the same speed. The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  226  rotates at a speed determined from the speed of the ring gear member  224  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The sun gear member  232  and the planetary gear set  240  rotate at the same speed as the output shaft  19 . The sun gear member  232 , and therefore the output shaft, rotates at a speed determined from the speed of the planet carrier assembly member  236  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The numerical value of the sixth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220  and  230 . 
     The seventh forward speed ratio is established with the engagement of the clutches  250  and  254 . The clutch  250  connects the ring gear member  224  to the sun gear member  242 . The clutch  254  connects the planet carrier assembly member  226  to the planet carrier assembly member  236 . The ring gear member  224  and the sun gear member  242  rotate at the same speed as the input shaft  17 . The planet carrier assembly members  226 ,  236  rotate at the same speed. The sun gear member  222  and the ring gear member  234  do not rotate. The planet carrier assembly member  226  rotates at a speed determined from the speed of the ring gear member  224  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The sun gear member  232  rotates at the same speed as the planet carrier assembly member  246 . The planet carrier assembly member  236  rotates at a speed determined from the speed of the sun gear member  232  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The ring gear member  244  rotates at the same speed as the output shaft  19 . The ring gear member  244 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  246 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The numerical value of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220 ,  230  and  240 . 
     As previously set forth, the truth table of FIG. 3 b  describes the combinations of engagements utilized for the seven forward speed ratios and reverse ratio. The truth table also provides an example of speed ratios that are available with the family member described above. These examples of speed ratios are determined utilizing the tooth ratios given in FIG. 3 b . The R 1 /S 1  value is the tooth ratio of the planetary gear set  220 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  230 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  240 . Also depicted in FIG. 3 b  is a chart representing the ratio steps between adjacent forward speed ratios and the reverse speed ratio. For example, the first to second ratio interchange has a step of 1.54. It can also be readily determined from the truth table of FIG. 3 b  that all of the single step forward ratio interchanges are of the single transition variety, as are the double step forward interchanges. 
     A powertrain  310 , shown in FIG. 4 a , includes the engine and torque converter  12 , a planetary transmission  314 , and the final drive mechanism  16 . The planetary transmission  314  includes an input shaft  17  continuously connected with the engine and torque converter  12 , a planetary gear arrangement  318 , and output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  318  includes three planetary gear sets  320 ,  330  and  340 . 
     The planetary gear set  320  includes a sun gear member  322 , a ring gear member  324 , and a planet carrier assembly member  326 . The planet carrier assembly member  326  includes a plurality of pinion gears  327  rotatably mounted on a carrier member  329  and disposed in meshing relationship with both the sun gear member  322  and the ring gear member  324 . 
     The planetary gear set  330  includes a sun gear member  332 , a ring gear member  334 , and a planet carrier assembly member  336 . The planet carrier assembly member  336  includes a plurality of pinion gears  337  rotatably mounted on a carrier member  339  and disposed in meshing relationship with both the sun gear member  332  and the ring gear member  334 . 
     The planetary gear set  340  includes a sun gear member  342 , a ring gear member  344 , and a planet carrier assembly member  346 . The planet carrier assembly member  346  includes a plurality of pinion gears  347  rotatably mounted on a carrier member  349  and disposed in meshing relationship with both the sun gear member  342  and the ring gear member  344 . 
     The planetary gear arrangement  318  also includes six torque-transmitting mechanisms  350 ,  352 ,  354 ,  356 ,  358  and  359 . The torque-transmitting mechanisms  350 ,  352 ,  354 ,  356  and  358  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanism  359  is a stationary-type torque transmitting mechanism, commonly termed brake or reaction clutch. 
     The input shaft  17  is continuously connected with the sun gear member  322 , and the output shaft  19  is continuously connected with the ring gear member  344 . The ring gear member  324  is continuously connected with the sun gear member  332  and the transmission housing  360  through the interconnecting member  370 . The planet carrier assembly member  336  is continuously connected with the sun gear member  342  through the interconnecting member  372 . 
     The sun gear member  322  is selectively connectable with the ring gear member  334  through the clutch  350 . The sun gear member  322  is selectively connectable with the planet carrier assembly member  346  through the clutch  352 . The planet carrier assembly member  326  is selectively connectable with the planet carrier assembly member  336  through the clutch  354 . The planet carrier assembly member  326  is selectively connectable with the ring gear member  334  through the clutch  356 . The planet carrier assembly member  346  is selectively connectable with the sun gear member  342  through the clutch  358 . The planet carrier assembly member  346  is selectively connectable with the transmission housing  360  through the brake  359 . 
     The truth tables given in FIGS. 4 b ,  5   b ,  6   b ,  7   b  and  8   b  show the engagement sequences for the torque-transmitting mechanisms to provide at least seven forward speed ratios and at least one reverse ratio. As shown and described above for the configuration in FIGS. 1 a ,  2   a  and  3   a , those skilled in the art will understand from the respective truth tables how the speed ratios are established through the planetary gear sets identified in the written description. 
     The truth table shown in FIG. 4 b  describes the engagement combination and the engagement sequence necessary to provide the reverse drive ratio and seven forward speed ratios. A sample of the numerical values for the ratios is also provided in the truth table of FIG. 4 b . These values are determined utilizing the ring gear/sun gear tooth ratios also given in FIG. 4 b . The R 1 /S 1  value is the tooth ratio for the planetary gear set  320 ; the R 2 /S 2  value is the tooth ratio for the planetary gear set  330 ; and the R 3 /S 3  value is the tooth ratio for the planetary gear set  340 . Also given in FIG. 4 b  is a chart describing the step ratios between the adjacent forward speed ratios and the reverse to first forward speed ratio. For example, the first to second forward speed ratio step is 1.67. It can be readily determined from the truth table of FIG. 4 b  that each of the forward single step ratio interchanges is a single transition shift, except the reverse to first step. The double step ratio interchanges are of the single shift variety as well. 
     Those skilled in the art will recognize that the numerical values of the reverse and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  320  and  340 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  320  and  330 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  320 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  330 . The numerical value of the fourth forward speed ratio is 1. The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  330  and  340 . The numerical value of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  320 ,  330  and  340 . 
     A powertrain  410 , shown in FIG. 5 a , includes the engine and torque converter  12 , a planetary transmission  414  and the final drive mechanism  16 . The planetary transmission  414  includes a planetary gear arrangement  418 , input shaft  17  and output shaft  19 . The planetary gear arrangement  418  includes three simple planetary gear sets  420 ,  430  and  440 . 
     The planetary gear set  420  includes a sun gear member  422 , a ring gear member  424 , and a planet carrier assembly  426 . The planet carrier assembly  426  includes a plurality of pinion gears  427  rotatably mounted on a carrier member  429  and disposed in meshing relationship with both the sun gear member  422  and the ring gear member  424 . 
     The planetary gear set  430  includes a sun gear member  432 , a ring gear member  434 , and a planet carrier assembly member  436 . The planet carrier assembly member  436  includes a plurality of pinion gears  437  rotatably mounted on a carrier member  439  and disposed in meshing relationship with both the sun gear member  432  and the ring gear member  434 . 
     The planetary gear set  440  includes a sun gear member  442 , a ring gear member  444 , and a planet carrier assembly member  446 . The planet carrier assembly member  446  includes a plurality of pinion gears  447  rotatably mounted on a carrier member  449  and disposed in meshing relationship with both the sun gear member  442  and the ring gear member  444 . 
     The planetary gear arrangement  418  also includes six torque-transmitting mechanisms  450 ,  452 ,  454 ,  456 ,  458  and  459 . The torque-transmitting mechanisms  450 ,  452 ,  454 ,  456  and  458  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanism  459  is a stationary-type torque transmitting mechanism, commonly termed brake or reaction clutch. 
     The input shaft  17  is continuously connected with the sun gear member  422 , and the output shaft  19  is continuously connected with the ring gear member  444 . The ring gear member  424  is continuously connected with the sun gear member  432  and the transmission housing  460  through the interconnecting member  470 . The ring gear member  434  is continuously connected with the sun gear member  442  through the interconnecting member  472 . 
     The sun gear member  422  is selectively connectable with the ring gear member  434  through the clutch  450 . The sun gear member  422  is selectively connectable with the planet carrier assembly member  446  through the clutch  452 . The planet carrier assembly member  426  is selectively connectable with the ring gear member  434  through the clutch  454 . The planet carrier assembly member  426  is selectively connectable with the planet carrier assembly member  436  through the clutch  456 . The planet carrier assembly member  436  is selectively connectable with the planet carrier assembly member  446  through the clutch  458 . The planet carrier assembly member  446  is selectively connectable with the transmission housing  460  through the brake  459 . 
     The truth table shown in FIG. 5 b  describes the engagement combination and sequence of the torque-transmitting mechanisms  450 ,  452 ,  454 ,  456 ,  458  and  459  that are employed to provide the reverse drive ratio and the seven forward speed ratios. It should be noted that the torque-transmitting mechanism  454  is engaged through the neutral condition to simplify the forward/reverse interchange. 
     Also given in the truth table of FIG. 5 b  is a set of numerical values that are attainable with the present invention utilizing the ring gear/sun gear tooth ratios shown. The R 1 /S 1  value is the tooth ratio of the planetary gear set  420 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  430 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  440 . As can also be determined from the truth table of FIG. 5 b , the single step forward interchanges are single transition shifts, as are the double step forward interchanges. 
     FIG. 5 b  also provides a chart of the ratio steps between adjacent forward ratios and between the reverse and first forward ratio. For example, the ratio step between the first and second forward ratios is 1.58. Those skilled in the art will recognize that the numerical values of the reverse and seventh forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  420  and  440 . The numerical values of the first, second, third and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  420 ,  430  and  440 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  430  and  440 . The numerical value of the fifth forward speed ratio is 1. 
     A powertrain  510 , shown in FIG. 6 a , includes an engine and torque converter  12 , a planetary gear transmission  514  and the final drive mechanism  16 . The planetary transmission  514  includes the input shaft  17 , a planetary gear arrangement  518  and the output shaft  19 . The planetary gear arrangement  518  includes three planetary gear sets  520 ,  530  and  540 . 
     The planetary gear set  520  includes a sun gear member  522 , a ring gear member  524 , and a planet carrier assembly  526 . The planet carrier assembly  526  includes a plurality of pinion gears  527  rotatably mounted on a carrier member  529  and disposed in meshing relationship with both the sun gear member  522  and the ring gear member  524 . 
     The planetary gear set  530  includes a sun gear member  532 , a ring gear member  534 , and a planet carrier assembly member  536 . The planet carrier assembly member  536  includes a plurality of pinion gears  537  rotatably mounted on a carrier member  539  and disposed in meshing relationship with both the sun gear member  532  and the ring gear member  534 . 
     The planetary gear set  540  includes a sun gear member  542 , a ring gear member  544 , and a planet carrier assembly member  546 . The planet carrier assembly member  546  includes a plurality of pinion gears  547  rotatably mounted on a carrier member  549  and disposed in meshing relationship with both the sun gear member  542  and the ring gear member  544 . 
     The planetary gear arrangement  518  also includes six torque-transmitting mechanisms  550 ,  552 ,  554 ,  556 ,  558  and  559 , each of which is a rotating type torque-transmitting mechanism, commonly termed clutch. 
     The input shaft  17  is continuously connected with the planet carrier assembly member  546 , and the output shaft  19  is continuously connected with the ring gear member  544 . The ring gear member  524  is continuously connected with the sun gear member  532  and the transmission housing  560  through the interconnecting member  570 . The planet carrier assembly member  536  is continuously connected with the ring gear member  544  through the interconnecting member  572 . 
     The planet carrier assembly member  526  is selectively connectable with the ring gear member  534  through the clutch  550 . The planet carrier assembly member  526  is selectively connectable with the sun gear member  542  through the clutch  552 . The planet carrier assembly member  526  is selectively connectable with the planet carrier assembly member  546  through the clutch  554 . The sun gear member  522  is selectively connectable with the ring gear member  534  through the clutch  556 . The sun gear member  522  is selectively connectable with the sun gear member  542  through the clutch  558 . The sun gear member  522  is selectively connectable with the planet carrier assembly member  546  through the clutch  559 . 
     The truth table shown in FIG. 6 b  describes the engagement sequence and combination of the torque-transmitting mechanisms to provide one reverse speed ratios and eight forward speed ratios. It should be noted that the torque-transmitting mechanism  550  can remain engaged through the neutral condition, thereby simplifying the forward/reverse interchange. It can also be determined from the truth table of FIG. 6 b  that all of the single step forward ratio interchanges are of the single transition variety, except the reverse to first step. The double step forward interchanges are single transition shifts as well. The chart of FIG. 6 b  describes the ratio steps between adjacent forward speed ratios and the ratio step between the reverse and first forward speed ratio. 
     Those skilled in the art, upon reviewing the truth table and the schematic representation of FIG. 6 a , can determine that the numerical values of the reverse and seventh forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  520  and  540 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  520  and  530 . The numerical values of the second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  520 ,  530  and  540 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  530 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  530  and  540 . The numerical value of the fifth forward speed ratio is 1. The numerical value of the eighth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  540 . 
     The sample speed ratios given in the truth table are determined utilizing the tooth ratio values also given in FIG. 6 b . The R 1 /S 1  value is the tooth ratio of the planetary gear set  520 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  530 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  540 . 
     A powertrain  610 , shown in FIG. 7 a , has the engine and torque converter  12 , a planetary transmission  614  and the final drive mechanism  16 . The planetary transmission  614  includes the input shaft  17 , a planetary gear arrangement  618  and the output shaft  19 . The planetary gear arrangement  618  includes three planetary gear sets  620 ,  630  and  640 . 
     The planetary gear set  620  includes a sun gear member  622 , a ring gear member  624 , and a planet carrier assembly  626 . The planet carrier assembly  626  includes a plurality of pinion gears  627  and  628  rotatably mounted on a carrier member  629  and disposed in meshing relationship with both the sun gear member  622  and the ring gear member  624 . 
     The planetary gear set  630  includes a sun gear member  632 , a ring gear member  634 , and a planet carrier assembly member  636 . The planet carrier assembly member  636  includes a plurality of pinion gears  637  rotatably mounted on a carrier member  639  and disposed in meshing relationship with both the sun gear member  632  and the ring gear member  634 . 
     The planetary gear set  640  includes a sun gear member  642 , a ring gear member  644 , and a planet carrier assembly member  646 . The planet carrier assembly member  646  includes a plurality of pinion gears  647  rotatably mounted on a carrier member  649  and disposed in meshing relationship with both the sun gear member  642  and the ring gear member  644 . 
     The planetary gear arrangement  618  also includes six torque-transmitting mechanisms  650 ,  652 ,  654 ,  656 ,  658  and  659 . The torque-transmitting mechanisms  650 ,  652 ,  654 ,  656  and  658  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanism  659  is a stationary-type torque transmitting mechanism, commonly termed brake or reaction clutch. 
     The input shaft  17  is continuously connected with the planet carrier assembly member  626 , and the output shaft  19  is continuously connected with the ring gear member  644 . The ring gear member  634  is continuously connected with the sun gear member  622  and the transmission housing  660  through the interconnecting member  670 . The sun gear member  632  is continuously connected with the planet carrier assembly member  646  through the interconnecting member  672 . 
     The planet carrier assembly member  626  is selectively connectable with the sun gear member  642  through the clutch  650 . The ring gear member  624  is selectively connectable with the sun gear member  632  through the clutch  652 . The ring gear member  624  is selectively connectable with the planet carrier assembly member  636  through the clutch  654 . The planet carrier assembly member  646  is selectively connectable with the sun gear member  642  through the clutch  656 . The planet carrier assembly member  636  is selectively connectable with the ring gear member  644  through the clutch  658 . The planet carrier assembly member  636  is selectively connectable with the transmission housing  660  through the brake  659 . 
     The truth table shown in FIG. 7 b  describes the combination of torque-transmitting mechanism engagements that will provide the reverse drive ratio and seven forward speed ratios, as well as the sequence of these engagements and interchanges. The torque-transmitting mechanisms  650  can be engaged through the neutral condition, thereby simplifying the forward/reverse interchange. 
     The ratio values given are by way of example and are established utilizing the ring gear/sun gear tooth ratios given in FIG. 7 b . For example, the R 1 /S 1  value is the tooth ratio of the planetary gear set  620 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  630 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  640 . The ratio steps between adjacent forward ratios and the reverse to first ratio are also given in FIG. 7 b.    
     Those skilled in the art will, upon reviewing the truth table of FIG. 7 b , will recognize that the numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  640 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  630  and  640 . The numerical values of the second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  620  and  630 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  620  and  640 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  620 . The numerical value of the fifth forward speed ratio is 1. The numerical value of the seventh forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  620 ,  630  and  640 . 
     A powertrain  710 , shown in FIG. 8 a , has the conventional engine and torque converter  12 , a planetary transmission  714 , and the conventional final drive mechanism  16 . The engine and torque converter  12  are drivingly connected with the planetary transmission  714  through the input shaft  17 . The planetary transmission  714  is drivingly connected with the final drive mechanism  16  through the output shaft  19 . The planetary transmission  714  includes a planetary gear arrangement  718  that has a first planetary gear set  720 , a second planetary gear set  730 , and a third planetary gear set  740 . 
     The planetary gear set  720  includes a sun gear member  722 , a ring gear member  724 , and a planet carrier assembly  726 . The planet carrier assembly  726  includes a plurality of pinion gears  727  rotatably mounted on a carrier member  729  and disposed in meshing relationship with both the sun gear member  722  and the ring gear member  724 . 
     The planetary gear set  730  includes a sun gear member  732 , a ring gear member  734 , and a planet carrier assembly member  736 . The planet carrier assembly member  736  includes a plurality of pinion gears  737  rotatably mounted on a carrier member  739  and disposed in meshing relationship with both the sun gear member  732  and the ring gear member  734 . 
     The planetary gear set  740  includes a sun gear member  742 , a ring gear member  744 , and a planet carrier assembly member  746 . The planet carrier assembly member  746  includes a plurality of pinion gears  747  rotatably mounted on a carrier member  749  and disposed in meshing relationship with both the sun gear member  742  and the ring gear member  744 . 
     The planetary gear arrangement  718  also includes six torque-transmitting mechanisms  750 ,  752 ,  754 ,  756 ,  758  and  759 . The torque-transmitting mechanisms  750 ,  752 ,  754 ,  756  and  758  are rotating type torque-transmitting mechanisms, commonly termed clutches. The torque-transmitting mechanism  759  is a stationary-type torque-transmitting mechanism, commonly termed brake or reaction clutch. 
     The input shaft  17  is continuously connected with the sun gear member  722 , and the output shaft  19  is continuously connected with the ring gear member  744 . The ring gear member  724  is continuously connected with the sun gear member  732  and the transmission housing  760  through the interconnecting member  770 . The ring gear member  734  is continuously connected with the sun gear member  742  through the interconnecting member  772 . 
     The sun gear member  722  is selectively connectable with the ring gear member  734  through the clutch  750 . The sun gear member  722  is selectively connectable with the planet carrier assembly member  746  through the clutch  752 . The planet carrier assembly member  726  is selectively connectable with the ring gear member  734  through the clutch  754 . The planet carrier assembly member  726  is selectively connectable with the planet carrier assembly member  736  through the clutch  756 . The planet carrier assembly member  736  is selectively connectable with the ring gear member  744  through the clutch  758 . The planet carrier assembly member  746  is selectively connectable with the transmission housing  760  through the brake  759 . 
     The truth table of FIG. 8 b  defines the torque-transmitting mechanism engagement sequence utilized for each of the forward speed ratios and the reverse speed ratio. Also given in the truth table is a set of numerical values that are attainable with the present invention utilizing the ring gear/sun gear tooth ratios given in FIG. 8 b . The R 1 /S 1  value is the tooth ratio of the planetary gear set  720 ; the R 2 /S 2  value is the tooth ratio of the planetary gear set  730 ; and the R 3 /S 3  value is the tooth ratio of the planetary gear set  740 . As can also be determined from the truth table of FIG. 8 b , the single step forward interchanges are single transition shifts, as are the double step interchanges in the forward direction. 
     FIG. 8 b  also provides a chart of the ratio steps between adjacent forward ratios and between the reverse and first forward ratio. For example, the ratio step between the first and second forward ratios is 1.63. Those skilled in the art will recognize that the numerical values of the reverse and seventh forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  720  and  740 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  720  and  730 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  720 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  730 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  730  and  740 . The numerical value of the fifth forward speed ratio is 1. The numerical value of the sixth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  720 ,  730  and  740 . 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.