Abstract:
A transmission is provided having a differential gear set with three input torque-transmitting mechanisms, such as friction clutches, to achieve torque flow through the differential gear set to a countershaft gearing arrangement. The transmission utilizes power-on shifts. By utilizing the torque ratio of the differential gear set, additional forward ratios are available with good step progression, reducing the number of countershaft gear sets and synchronizers necessary in comparison to a dual-clutch transmission providing the same number of ratios. A shorter axial length is thus attainable.

Description:
TECHNICAL FIELD 
     The invention relates to a multi-speed transmission having both a differential gear set and a countershaft gearing arrangement. 
     BACKGROUND OF THE INVENTION 
     A typical multi-speed, dual clutch transmission uses a combination of two friction clutches and several dog clutch/synchronizers to achieve “power-on” or dynamic shifts by alternating between one friction clutch and the other, with the synchronizers being “pre-selected” for the oncoming ratio prior to actually making the dynamic shift. “Power-on” shifting means that torque flow from the engine need not be interrupted prior to making the shift. This concept typically uses countershaft gears with a different, dedicated gear pair or set to achieve each forward speed ratio (with the exception of being able to achieve a direct drive ratio in a rear wheel drive application). Accordingly, the total number of gears required in this typical design is two times the number of forward speeds, plus three for reverse. This necessitates a large number of required gear pairs, especially in transmissions that have a relatively large number of forward speed ratios. 
     SUMMARY OF THE INVENTION 
     A transmission is provided having a differential gear set with three input torque-transmitting mechanisms, such as friction clutches, to achieve torque flow through the differential gear set to a countershaft gearing arrangement utilizing power-on shifts. In comparison with a convention dual-clutch transmission, one of the input torque-transmitting mechanisms and the differential gear set are added. By utilizing the torque ratio of the differential gear set, additional torque ratios are available with good step progression, reducing the number of countershaft gear sets and synchronizers necessary in comparison to a dual-clutch transmission providing the same number of torque ratios. A shorter axial length is thus attainable. 
     Specifically, a transmission is provided including an input member and an output member. A differential gear set has first, second and third members and a first, a second and a third torque-transmitting mechanism are each selectively engagable to connect the input member with a respective different one of the differential gear set members. A countershaft gearing arrangement is operatively connected to the differential gear set. The countershaft gearing arrangement includes a plurality of sets of co-planar intermeshing gears, a plurality of shafts axially and a plurality of synchronizers selectively engagable to transfer torque from the differential gear set to the output member along the shafts and the sets of co-planar, intermeshing gears. 
     By providing three torque-transmitting mechanisms, additional torque ratios are achieved with respect to the dual-clutch transmission. Specifically, the first torque-transmitting mechanism is selectively engagable along with a first of the synchronizers to establish a first torque ratio between the input member and the output member. The second torque-transmitting mechanism is selectively engagable along with a second of the synchronizers to establish a second torque ratio between the input member and the output member. The third torque-transmitting mechanism is selectively engagable along with both of the first and second synchronizers to establish the third torque ratio between the input member and the output member. The numerical value of the third torque ratio is less than the first torque ratio and greater than the second torque ratio. The third torque ratio is a combined ratio determined by the torque ratio of the differential gear set as well as the torque ratios of the active sets of co-planar, intermeshing gears. The first and second torque ratios, however, are determined based only on the torque ratios of the active sets of co-planar, intermeshing gears. Thus, the sets of co-planar, intermeshing gears through which torque is carried during engagement of the first or the second torque-transmitting mechanism are reused when the third torque-transmitting mechanism is engaged to provide the different, third torque ratio. In other words, the torque ratio of the differential gear set does not affect the first and second ratios, but allows a torque ratio between the first and second torque ratios (i.e., the third torque ratio). 
     Within the scope of the invention, the differential gear set may be a beveled gear set, a simple pinion or a double pinion planetary gear set. 
     The countershaft gearing arrangement may be a two-axis design, having only one countershaft, or a three-axis design, having two offset countershafts. 
     In another aspect of the invention, a reverse torque ratio may be achieved utilizing a dedicated set of co-planar, intermeshing gears. However, in another embodiment, a reverse torque ratio is achieved by adding a synchronizer that selectively connects one of the members of the differential gear set to a stationary member to obtain a reverse torque ratio, thus eliminating the need for a dedicated set of intermeshing gears. Preferably, in the latter embodiment, the differential gear set is a double pinion planetary gear set and the additional synchronizer grounds the ring gear member to a stationary member such as the transmission housing. 
     The above features and advantages and other 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  is a schematic representation of a first embodiment of a transmission in accordance with the invention; 
         FIG. 2  is a truth table listing the engaged torque-transmitting mechanisms and synchronizers for selected torque ratios achieved by the transmission of  FIG. 1 ; 
         FIG. 3  is a listing of torque ratios and step ratios achieved by the transmission of  FIG. 1  corresponding with the truth table of  FIG. 2 ; 
         FIG. 4  is a schematic representation of a second embodiment of a transmission in accordance with the invention; 
         FIG. 5  is a schematic representation of a third embodiment of a transmission in accordance with the invention; 
         FIG. 6  is a truth table listing the engaged torque-transmitting mechanisms and synchronizers for selected torque ratios of the transmission of  FIG. 5 ; 
         FIG. 7  is a ratio chart listing the torque ratios and ratio steps achieved by the transmission of  FIG. 5  corresponding with the truth table of  FIG. 6 ; and 
         FIG. 8  is a schematic representation of a fourth embodiment of a transmission in accordance with the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components, in  FIG. 1  a multi-speed transmission  10  is depicted. The transmission  10  includes an input member  12  and output member  14 . In this embodiment, the input member  12  and the output member  14  are shafts, and will be referred to as such. Those skilled in the art will appreciate that the input and output members  12 ,  14  may be components other than shafts. The input shaft  12  is continuously connected with an engine (not shown). The output shaft  14  is continuously connected with the final drive unit (not shown). The transmission  10  includes a countershaft gearing arrangement  17  that includes intermediate shafts, countershafts, co-planar intermeshing gear sets and selectively engagable synchronizers as will be described herein. For instance, the countershaft gearing arrangement  17  includes an intermediate shaft  16  and an intermediate shaft  18 , which is a sleeve shaft concentric with the intermediate shaft  16 . The intermediate shafts  18  and  16  are referred to in the claims as the first and second intermediate shafts, respectively. The countershaft gearing arrangement  17  further includes a countershaft  20  and a countershaft  22 . Countershaft  20  is referred to in the claims as the second countershaft and countershaft  22  is referred to in the claims as the first countershaft. The countershafts  20 ,  22  are both spaced from and parallel with the input shaft  12 , the output shaft  14  and the intermediate shafts  16 ,  18 . 
     A differential gear set  30 , which is a simple planetary gear set, is connected between the input shaft  12  and the output shaft  14 . The differential gear set  30  includes sun gear member  32  (labeled S) connected for common rotation with the intermediate shaft  16 , a ring gear member  34  (labeled R) connected for common rotation with the intermediate shaft  18 , and a carrier member  37  which rotatably supports a set of pinion gears  39  (labeled P) which intermesh with both the sun gear member  32  and the ring gear member  34 . 
     The countershaft gearing arrangement  17  also includes co-planar, intermeshing gear sets  40 ,  50 ,  60 ,  70  and  80 . Gear set  40  includes gears  42 ,  44 ,  46  and  48 . Gear  42  is connected for common rotation with the intermediate shaft  18  and intermeshes with gear  44 , which is rotatable about and selectively connectable with the countershaft  22 . Gear  46  is rotatable about and selectively connectable with the countershaft  20 . An idler gear  48  rotates about idler axis I and intermeshes with both the gear  42  and gear  46 . (Gear  48  is shown intermeshing only with gear  46  but those skilled in the art will readily understand that gear  48  is actually placed adjacent and between gears  42  and  46  to allow torque transfer therebetween). 
     Co-planar gear set  50  includes gear  52  and gear  54 . Gear  52  is connected for common rotation with intermediate shaft  18  and intermeshes with gear  54 , which rotates about and is selectively connectable with countershaft  22 . 
     Gear set  60  includes co-planar intermeshing gears  62  and  66 . Gear  62  is connected for common rotation with the intermediate shaft  18  and intermeshes with gear  66 , which is rotatable about and selectively connectable with countershaft  20 . 
     Gear set  70  includes co-planar, intermeshing gears  72  and  74 . Gear  72  rotates about and is selectively connectable with intermediate shaft  16 . Gear  72  intermeshes with gear  74 , which is connected for common rotation with countershaft  22 . 
     Gear set  80  includes gear  82 , gear  84  and gear  86 . Gear  82  is connected for common rotation with the output shaft  14  and is selectively connectable with the intermediate shaft  16 . Gear  82  intermeshes with both gear  84  and gear  86 . Gear  84  is connected for common rotation with the countershaft  22 . Gear  86  is connected for common rotation with the countershaft  20 . 
     The transmission  10  includes a variety of torque-transmitting mechanisms or devices including input clutch  90 , input clutch  91 , and input clutch  92 . In the claims, input clutch  90  is referred to as the first torque-transmitting mechanism, input clutch  92  is referred to as the second torque-transmitting mechanism and input clutch  91  is referred to as the third torque-transmitting mechanism. Input clutch  90  is selectively engagable to connect the input shaft  12  with the ring gear member  34 . Input clutch  91  is selectively engagable to connect the input shaft  12  with the carrier member  37 . Input clutch  92  is selectively engagable to connect the input shaft  12  with the sun gear member  32  and the intermediate shaft  16 . The transmission  10  further includes a plurality of selectively engagable synchronizers  93 ,  94 ,  95 ,  96 ,  97 , and  98 . Synchronizer  93  is selectively engagable to connect gear  44  with countershaft  22  for common rotation therewith. Synchronizer  94  is selectively engagable to connect gear  72  with intermediate shaft  16  for common rotation therewith. Synchronizer  93  is referred to in the claims as the first synchronizer. Synchronizer  94  is referred to in the claims as the second synchronizer. Synchronizer  95  is selectively engagable to connect gear  54  with countershaft  22  for common rotation therewith. Synchronizer  96  is selectively engagable to connect the gear  82 , and therefore the output shaft  14 , with the intermediate shaft  16  for common rotation therewith. Synchronizer  97  is selectively engagable to connect gear  66  with countershaft  20  for common rotation therewith. Synchronizer  98  is selectively engagable to connect gear  46  with countershaft  20  for common rotation therewith. 
     The transmission  10  is capable of transmitting torque from the input shaft  12  to the output shaft  14  in at least seven forward torque ratios and one reverse torque ratio as indicated in the truth table of  FIG. 2 . Up to four additional forward torque ratios (two of which are indicated in  FIG. 2 ) may be achieved for a total of eleven forward torque ratios, as will be described below. Each of the forward torque ratios and the reverse torque ratio is attained by engagement of one of the first, second, third torque-transmitting mechanism or input clutches  90 ,  91 ,  92  and one or more of the synchronizers  93 - 98 . Those skilled in the art will readily understand that a different speed ratio is associated with each torque ratio. Thus, eleven forward speed ratios may be attained by the transmission  10 . 
     To establish the reverse torque ratio (Gear REV), the input clutches and synchronizers are selected as set forth in the table of  FIG. 2 . The input clutch  90  and synchronizer  98  are engaged. The input clutch  90  connects the ring gear member  34  with the input shaft  12 . Synchronizer  98  connects gear  46  for common rotation with countershaft  20 . Torque is thus transferred from the input shaft  12  through the ring gear member  34  from gear  42  and intermediate shaft  18  to gear  46  and countershaft  20  through idler gear  48 . Torque is then transferred from gear  86  to gear  82  and thereby to the output shaft  14 . 
     Two additional reverse torque ratios not indicated in the truth table of  FIG. 2  are optionally available. The first optional reverse torque ratio is achieved by a combination of engagement synchronizers listed for the reverse torque ratio listed as Gear REV and the forward torque ratio listed as Gear  2  in  FIG. 2  (i.e., synchronizers  94  and  98 ), as well as the input clutch  91 . In this arrangement, torque flows through carrier member  37 , pinion gears  39  and ring gear member  34  to intermediate shaft  18 . The torque is then transferred through reverse gear set  40  to countershaft  20 , due to engagement of synchronizer  98 , and then to output shaft  14  through gear set  80 . Torque also flows through carrier member  37 , pinion gears  39  and sun gear member  32  to intermediate shaft  16 , through gear set  70  due to engagement of synchronizer  94 , and then from countershaft  22  to output shaft  14  through gear set  80 . 
     The second optional reverse torque ratio is achieved by a combination engagement of the synchronizers listed in  FIG. 2  for the reverse torque ratio listed as Gear REV and the forward torque ratio listed in  FIG. 2  as Gear  5  (i.e., synchronizers  96  and  98 ), as well as input clutch  91 . In this arrangement, torque flows through carrier member  37 , pinion gears  39  and ring gear member  34  to intermediate shaft  18 . The torque is then transferred through reverse gear set  40  to countershaft  20 , due to engagement of synchronizer  98 , and then to output shaft  14  through gear set  80 . Torque also flows through carrier member  37 , pinion gears  39  and sun gear member  32  to intermediate shaft  16  directly to output shaft  14  via engagement of synchronizer  96 . 
     A first forward torque ratio (listed as Gear  1  in the truth table of  FIG. 2 ), is achieved by engaging the input clutch  90  and synchronizer  93 . In this arrangement, torque is transferred from the input shaft  12  through the ring gear member  34  to the intermediate shaft  18  by engagement of the input clutch  90  and through gear set  40  to the countershaft  22  by engagement of synchronizer  93 . Torque is then transferred to the output shaft  14  through the gear set  80 . 
     A second optional forward torque ratio (indicated as Gear  1 ′ in  FIG. 2 ), may be obtained by engagement of input clutch  91  and synchronizers  93  and  94 . Accordingly, to shift from Gear  1  to Gear  1 ′, input clutch  90  is disengaged, input clutch  91  is engaged and synchronizer  94  is engaged while synchronizer  93  remains engaged. Thus, in the optional forward torque ratio  1 ′, torque flows from the input shaft  12  through the carrier member  37  of differential gear set  30  by engagement of input clutch  91  and thereby through the sun gear  32  and the ring gear  34  to the intermediate shaft  16  and the intermediate shaft  18 , respectively. The torque along intermediate shaft  16  is transferred through gear set  70  to countershaft  22  by engagement of synchronizer  94  and through the gear set  80  to output shaft  14 . The torque on intermediate shaft  18  is transferred to countershaft  22  through gear set  40  by engagement of synchronizer  93 . Torque is then transferred through gear set  80  to output shaft  14 . As noted in  FIG. 2 , in the torque ratio for Gear  1 , synchronizer  94  is open, i.e., is not transmitting torque. Accordingly, synchronizer  94  may be pre-selected to the necessary position of the on-coming torque ratio for Gear  1 ′ (or Gear  2 ) prior to actually shifting the torque path via the input clutches  90 ,  91 ,  92 , as indicated in  FIG. 2 . 
     A subsequent forward torque ratio, indicated as Gear  2  in  FIG. 2 , is established by engagement of input clutch  92  and synchronizer  94 . Gear  2  may be achieved directly from Gear  1  or from Gear  1 ′ if Gear  1 ′ is selected after Gear  1 . Either instance may be achieved without mechanical tie-up of the transmission  10 . In Gear  2 , torque is transferred from the input shaft  12  to the intermediate shaft  16  via the engaged input clutch  92 . Torque is transferred along gear set  70 , countershaft  22  and gear set  80  to output shaft  14  due to engagement of synchronizer  94 . 
     The subsequent torque ratio, indicated as Gear  3  in the truth table of  FIG. 2 , is established by the engagement of the input clutch  91 , synchronizer  94  and synchronizer  95 . Thus, in shifting from Gear  2  to Gear  3 , input clutch  92  is released and input clutch  91  is engaged. Synchronizer  94  remains engaged and synchronizer  95 , which was open in Gear  2 , is engaged in Gear  3 . The input clutch  91  directs torque through carrier member  37  of the differential gear set  30  and pinion gears  39  to both the intermediate shaft  16  and  18  via the sun gear member  32  and ring gear member  34 , respectively. The torque carried along intermediate shaft  16  is transferred to countershaft  22  through gear set  70  and then to output shaft  14  through gear set  80  due to engagement of synchronizer  94 . Torque carrier along intermediate shaft  18  is transferred to countershaft  22  through gear set  50  due to engagement of synchronizer  95  and to output shaft  14  though gear set  80 . 
     The next subsequent forward torque ratio, indicated as Gear  4  in the truth table of  FIG. 2 , is established with the engagement of the input clutch  90  and synchronizer  95 . Thus, in shifting from Gear  3  to Gear  4 , input clutch  91  and synchronizer  94  is released while input clutch  90  is engaged and synchronizer  95  remains engaged. Torque is transferred from the input shaft  12  to intermediate shaft  18  through ring gear  34  due to engaged input clutch  90 . Torque is then transferred through gear set  50  to countershaft  22  due to engagement of synchronizer  95 . Torque is transferred through gear set  80  to output shaft  14 . 
     The next subsequent torque ratio may optionally be achieved in Gear  4 ′, or alternatively, a shift may be made from Gear  4  directly to Gear  5 . Assuming a shift is made from Gear  4  to Gear  4 ′, input clutch  91  is engaged along with synchronizers  95  and  96 . Thus, in shifting from Gear  4  to Gear  4 ′, input clutch  90  is released while input clutch  91  is engaged, synchronizer  95  remains engaged and synchronizer  96  is engaged. Torque is transferred from input shaft  12  through the differential gear set  30  via engagement of input clutch  91  and to the intermediate shafts  16  and  18 . The torque carried on intermediate shaft  16  is transferred to the output shaft  14  due to engagement of synchronizer  96 , which operatively connects the output shaft  14  and gear  82  to intermediate shaft  16 . The torque carried on intermediate shaft  18  is transferred through gear set  50  to countershaft  22  and through gear set  80  to the output shaft  14  due to the engagement of synchronizer  95 . 
     A subsequent forward torque ratio indicated as Gear  5  in  FIG. 2 , is established with the engagement of input clutch  92  and synchronizer  96 . If Gear  5  is achieved in a shift from Gear  4 ′, input clutch  91  is released while input clutch  92  is engaged, with synchronizer  96  remaining engaged. Alternatively, if Gear  5  is achieved in a shift from Gear  4 , input clutch  90  is released while input clutch  92  is engaged and synchronizer  95  is released while synchronizer  96  is engaged. Torque is transferred from the input shaft  12  along the intermediate shaft  16  directly to the output shaft  14  due to engagement of the input clutch  92  and synchronizer  96 . Thus, a direct drive ratio is achieved, with the speed and torque of the output shaft  14  and the speed and torque of the input shaft  12  being equal. 
     A subsequent forward torque ratio indicated as Gear  6  in the truth table of  FIG. 2  is established with the engagement of input clutch  91  and synchronizers  96  and  97 . Thus, in shifting from Gear  5  to Gear  6 , input clutch  92  is released while input clutch  91  is engaged with synchronizer  96  remaining engaged and synchronizer  97  being engaged. Torque is transferred from the input shaft  12  through the differential gear set  30  by engagement of the input clutch  91  to both the intermediate shafts  16  and  18  through the sun gear member  32  and the ring gear member  34 , respectively. The torque carried on intermediate shaft  16  is transferred to the output shaft  14  by engagement of the synchronizer  96 . The torque carrier on the intermediate shaft  18  is transferred via the gear set  60  by engagement of synchronizer  97  to the countershaft  20  and then through gear set  80  to output shaft  14 . 
     To establish the next subsequent torque ratio, indicated as Gear  7  in the truth table of  FIG. 2 , input clutch  90  is engaged and synchronizer  97  is engaged. Thus, to shift from Gear  6  to Gear  7 , input clutch  91  is released while input clutch  90  is engaged with synchronizer  97  remaining engaged. Torque is transferred from the input shaft  12  through input clutch  90  and ring gear member  34  to the intermediate shaft  18 . Torque is then transferred through gear set  60  due to engagement of synchronizer  97  along countershaft  20  through gear set  80  to output shaft  14 . 
     In addition to the nine forward torque ratios indicated in the truth table of  FIG. 2 , two additional forward torque ratios are achievable for a total of eleven forward torque ratios. One additional forward torque ratio is numerically achieved between Gear  1 ′ and Gear  2  by combining engagement of the synchronizers indicated in Gear  1  and Gear  5  in the truth table of  FIG. 2 , along with input clutch  91 . Thus, an optional torque ratio, which may be referred to as Gear  1 ″ with a numerical value between that of Gear  1 ′ and Gear  2 ′ is achieved by engagement of input clutch  91  and synchronizers  93  and  96 . Another optional torque ratio not shown in the truth table of  FIG. 2  occurs numerically between Gear  4 ′ and Gear  5  and may be referred to as Gear  4 ″. Gear  4 ″ is achieved by a combination of engagement of the synchronizers indicated in the forward Gears  2  and  7  in the truth table of  FIG. 2 , along with input clutch  91 . Thus, Gear  4 ″ occurs by engagement of input clutch  91  and synchronizers  94  and  97 . 
     Referring to  FIG. 3 , torque ratios (i.e., the ratio of torque of the output member  14  to the input member  12 ) corresponding with each of the Gears shown in the truth table of  FIG. 2  are listed. These torque ratios are achieved utilizing the following sample component torque ratios which, in turn, are dependent on tooth counts of the gears of the transmission  10 : the ring gear member/sun gear member differential gear set torque ratio is 1.86; the torque ratio of gear  44  to gear  42  is 2.60; the torque ratio of gear  46  to gear  42  (transferred through idler gear  48 ) is 2.25; the torque ratio of gear  50  to gear  52  is 0.84; the torque ratio of gear  66  to gear  62  is 0.41; the torque ratio of gear  72  to gear  74  is 1.57; the torque ratio of gear  82  to either gear  84  or gear  86  is 1.57. The ratio steps between subsequent torque ratios are indicated in  FIG. 3 , with an overall torque ratio of 6.40. It is apparent from the truth table of  FIG. 2  and the ratio chart of  FIG. 3  that torque ratios that are achieved utilizing the input clutch  91  (i.e., with input clutch  91  in an engaged state) have a numerical value between subsequent on-coming and off-going torque ratios. Thus, by utilizing the input clutch  91  and the differential gear set  30 , additional torque ratios are achieved than would be achievable with only the input clutches  90  and  92 , as the latter result in torque ratios dependant only on the ratios of the countershaft gear sets and not of the differential gear set  30 . The step from Gear  1  to Gear  2  is 1.65 while the step from Gear  1 ′ to Gear  2  is 1.43 (indicated in brackets). The step from Gear  4  to Gear  5  is 1.31 while the step from Gear  4 ′ to Gear  5  is 1.20 (indicated in brackets). 
     Second Embodiment 
     Referring to  FIG. 4  a multi-speed transmission  100  is depicted. The transmission  100  includes an input member  12  and an output member  14 . In this embodiment, the input member  12  and the output member  14  are shafts, and will be referred to as such. Those skilled in the art will appreciate that the input and output members  12 ,  14  may be components other than shafts. The input shaft  12  is continuously connected with an engine (not shown). The output shaft  14  is continuously connected with the final drive unit (not shown). The transmission  100  includes a countershaft gearing arrangement  117  that includes intermediate shafts, a countershaft, co-planar intermeshing gear sets and selectively engagable synchronizers as will be described herein. For instance, the countershaft gearing arrangement  117  includes an intermediate shaft  116  and an intermediate shaft  118 , which is a sleeve shaft concentric with the intermediate shaft  116 . The intermediate shafts  118  and  116  are referred to in the claims as the first and second intermediate shafts, respectively. The countershaft gearing arrangement  117  further includes a countershaft  122 . Countershaft  122  is referred to in the claims as the first countershaft. The countershaft  122  is both spaced from and parallel with the input shaft  12 , the output shaft  14  and the intermediate shafts  116 ,  118 . 
     A differential gear set  130 , which is a simple planetary gear set, is connected between the input shaft  12  and the output shaft  14 . The differential gear set  130  includes sun gear member  132  (labeled S) connected for common rotation with the intermediate shaft  116 , a ring gear member  134  (labeled R) connected for common rotation with the intermediate shaft  118 , and a carrier member  137  which rotatably supports a set of pinion gears  139  (labeled P) which intermesh with both the sun gear member  132  and the ring gear member  134 . 
     The countershaft gearing arrangement  117  also includes co-planar, intermeshing gear sets  140 ,  141 ,  150 ,  160 ,  170  and  180 . Gear set  140  includes gears  142  and  144 . Gear  142  is connected for common rotation with the intermediate shaft  118  and intermeshes with gear  144 , which is rotatable about and selectively connectable with the countershaft  122 . Gear set  141  includes gear  145 , gear  146  and idler gear  148 . Gear  146  is rotatable about and selectively connectable with the countershaft  122 . Idler gear  148  rotates about idler axis I and intermeshes with both the gear  145  and gear  146 . (Gear  148  is shown intermeshing only with gear  146  but those skilled in the art will readily understand that gear  148  is actually placed adjacent and between gears  145  and  146  to allow torque transfer therebetween). 
     Co-planar gear set  150  includes gear  152  and gear  154 . Gear  152  is connected for common rotation with intermediate shaft  118  and intermeshes with gear  154 , which rotates about and is selectively connectable with countershaft  122 . 
     Gear set  160  includes co-planar intermeshing gears  162  and  164 . Gear  162  is connected for common rotation with the intermediate shaft  118  and intermeshes with gear  164 , which is rotatable about and selectively connectable with countershaft  122 . 
     Gear set  170  includes co-planar, intermeshing gears  172  and  174 . Gear  172  rotates about and is selectively connectable with intermediate shaft  116 . Gear  172  intermeshes with gear  174 , which is connected for common rotation with countershaft  122 . 
     Gear set  180  includes gear  182  and gear  184 . Gear  182  is connected for common rotation with the output shaft  14  and is selectively connectable with the intermediate shaft  116 . Gear  182  intermeshes with gear  184 . Gear  184  is connected for common rotation with the countershaft  122 . 
     The transmission  100  includes a variety of torque-transmitting mechanisms or devices including input clutch  190 , input clutch  191 , and input clutch  192 . In the claims, input clutch  190  is referred to as the first torque-transmitting mechanism, input clutch  192  is referred to as the second torque-transmitting mechanism and input clutch  191  is referred to as the third torque-transmitting mechanism. Input clutch  190  is selectively engagable to connect the input shaft  12  with the ring gear member  134 . Input clutch  191  is selectively engagable to connect the input shaft  12  with the carrier member  137 . Input clutch  192  is selectively engagable to connect the input shaft  12  with the sun gear member  132  and the intermediate shaft  116 . The transmission  100  further includes a plurality of selectively engagable synchronizers  193 ,  194 ,  195 ,  196 ,  197 , and  198 . Synchronizer  193  is selectively engagable to connect gear  144  with countershaft  122  for common rotation therewith. Synchronizer  193  if referred to in the claims as the first synchronizer. Synchronizer  194  is selectively engagable to connect gear  172  with intermediate shaft  116  for common rotation therewith. Synchronizer  194  is referred to in the claims as the second synchronizer. Synchronizer  195  is selectively engagable to connect gear  154  with countershaft  122  for common rotation therewith. Synchronizer  196  is selectively engagable to connect the gear  182 , and therefore the output shaft  14 , with the intermediate shaft  116  for common rotation therewith. Synchronizer  197  is selectively engagable to connect gear  164  with countershaft  122  for common rotation therewith. Synchronizer  198  is selectively engagable to connect gear  146  with countershaft  122  for common rotation therewith. 
     The transmission  100  is capable of transmitting torque from the input shaft  12  to the output shaft  14  at the nine forward torque ratios and one reverse torque ratio indicated in  FIG. 2 . The two additional forward torque ratios and the two extra reverse torque ratios described above with respect to transmission  10  of  FIG. 1  may be achieved for a total of eleven forward torque ratios and three reverse torque ratios. Those skilled in the art will readily understand how these torque ratios are achieved, based on the description of the transmission  10 . 
     Third Embodiment 
     Referring to  FIG. 5  a multi-speed transmission  200  is depicted. The transmission  200  includes an input member  12  and output member  14 . In this embodiment, the input member  12  and the output member  14  are shafts, and will be referred to as such. Those skilled in the art will appreciate that the input and output members  12 ,  14  may be components other than shafts. The input shaft  12  is continuously connected with an engine (not shown). The output shaft  14  is continuously connected with the final drive unit (not shown). The transmission  200  includes a countershaft gearing arrangement  217  that includes intermediate shafts, countershafts, co-planar intermeshing gear sets and selectively engagable synchronizers as will be described herein. For instance, the countershaft gearing arrangement  217  includes an intermediate shaft  216  and an intermediate shaft  218 , which is a sleeve shaft concentric with the intermediate shaft  216 . The intermediate shafts  218  and  216  are referred to in the claims as the first and second intermediate shafts, respectively. The countershaft gearing arrangement  217  further includes a countershaft  220  and a countershaft  222 . Countershaft  222  is referred to in the claims as the second countershaft and countershaft  220  is referred to in the claims as the first countershaft. The countershafts  220 ,  222  are both spaced from and parallel with the input shaft  12 , the output shaft  14  and the intermediate shafts  216 ,  218 . 
     A differential gear set  230 , which is a double-pinion planetary gear set, is connected between the input shaft  12  and the output shaft  14 . The differential gear set  230  includes sun gear member  232  (labeled S) connected for common rotation with the intermediate shaft  216 , a ring gear member  234  (labeled R), and a carrier member  237  connected for common rotation with the intermediate shaft  218  and which rotatably supports two sets of pinion gears  238 ,  239  (labeled P 1  and P 2 , respectively). Pinion gears  238  intermesh with the sun gear member  232  and with the pinion gears  239 . Pinion gears  239  intermesh with the ring gear member  234 . 
     The countershaft gearing arrangement  217  also includes co-planar, intermeshing gear sets  240 ,  250 ,  260 ,  270  and  280 . Gear set  240  includes gears  242  and  246 . Gear  242  is connected for common rotation with the intermediate shaft  218  and intermeshes with gear  246 , which is rotatable about and selectively connectable with the countershaft  220 . 
     Co-planar gear set  250  includes gear  252  and gear  254 . Gear  252  is connected for common rotation with intermediate shaft  218  and intermeshes with gear  254 , which rotates about and is selectively connectable with countershaft  222 . 
     Gear set  260  includes co-planar intermeshing gears  262  and  266 . Gear  262  is connected for common rotation with the intermediate shaft  216  and intermeshes with gear  266 , which is rotatable about and selectively connectable with countershaft  220 . 
     Gear set  270  includes co-planar, intermeshing gears  272  and  274 . Gear  272  is connected for common rotation with intermediate shaft  216 . Gear  272  intermeshes with gear  274 , which rotates about and is selectively connectable with countershaft  222 . 
     Gear set  280  includes gear  282 , gear  284  and gear  286 . Gear  282  is connected for common rotation with the output shaft  14  and is selectively connectable with the intermediate shaft  216 . Gear  282  intermeshes with both gear  284  and gear  286 . Gear  284  is connected for common rotation with the countershaft  222 . Gear  286  is connected for common rotation with the countershaft  220 . 
     The transmission  200  includes a variety of torque-transmitting mechanisms or devices including input clutch  290 , input clutch  291 , and input clutch  292 . In the claims, input clutch  290  is referred to as the first torque-transmitting mechanism, input clutch  292  is referred to as the second torque-transmitting mechanism and input clutch  291  is referred to as the third torque-transmitting mechanism. Input clutch  290  is selectively engagable to connect the input shaft  12  with the sun gear member  232 . Input clutch  291  is selectively engagable to connect the input shaft  12  with the ring gear member  234 . Input clutch  292  is selectively engagable to connect the input shaft  12  with the carrier member  237 . The transmission  200  further includes a plurality of selectively engagable synchronizers  293 ,  294 ,  295 ,  296 ,  297 , and  298 . Synchronizer  293  is selectively engagable to connect gear  266  with countershaft  220  for common rotation therewith. Synchronizer  293  is referred to in the claims as the first synchronizer. Synchronizer  294  is selectively engagable to connect gear  254  with countershaft  222  for common rotation therewith. Synchronizer  294  is referred to in the claims as the second synchronizer. Synchronizer  295  is selectively engagable to connect gear  282 , and therefore the output shaft  14 , with intermediate shaft  216  for common rotation therewith. Synchronizer  296  is selectively engagable to connect the gear  246  with the countershaft  220  for common rotation therewith. Synchronizer  297  is selectively engagable to connect gear  274  with countershaft  220  for common rotation therewith. Synchronizer  298  is selectively engagable to ground the ring gear member  234  with stationary transmission housing  299 . Synchronizer  298  is referred to in the claims as the additional synchronizer. 
     The transmission  200  is capable of transmitting torque from the input shaft  12  to the output shaft  14  in at least seven forward torque ratios and one reverse torque ratio, as indicated in the truth table of  FIG. 6 . Up to four additional forward torque ratios (two of which are indicated in  FIG. 6 ) may be achieved for a total of eleven forward torque ratios. The other two additional forward torque ratios are achieved in the same manner as ratios referred to as  1 ″ and  4 ″ in the description of the transmission  10  of  FIG. 1  (i.e., ratio  1 ″ is achieved by combining the engaged synchronizers of Gears  1  and  5  along with input clutch  291 , and ratio  4 ″ is achieved by combining the engaged synchronizers of Gears  2  and  7 , along with input clutch  291 ). Those skilled in the art will readily understand how the torque ratios of  FIG. 6  are achieved based on the description of transmission  10 . 
     With respect to the reverse torque ratio REV, this ratio is achieved by engaging input clutch  292 , and synchronizers  293  and  298 . Because the ring gear member  234  is grounded by engaging synchronizer  298 , the torque provided to the carrier member  237  via application of input clutch  292  is delivered through pinion gears  238  and  239  such that intermediate shaft  216  rotates in an opposite direction as input shaft  12 . The torque fed through gear set  260  via engagement of synchronizer  293  is then delivered from countershaft  220  through gear set  280  to output shaft  14  such that output shaft  14  rotates in a direction opposite that of input shaft  12 . Utilizing synchronizer  298  in combination with the double-pinion planetary gear set  230  to provide the reverse torque ratio REV allows a separate, dedicated plane of reversing gears to be eliminated. 
     Referring to  FIG. 7 , the torque ratios and ratio steps for each of the nine forward torque ratios and the reverse torque ratio indicated in  FIG. 6  are shown. The step from Gear  1  to Gear  2  is 1.51 while the step from Gear  1 ′ to Gear  2  is 1.27 (shown in brackets). The step from Gear  4  to Gear  5  is 1.38 while the step from Gear  4 ′ to Gear  5  is 1.20 (shown in brackets). Optionally, up to four additional reverse ratios may be achieved by engagement of input clutch  292  and synchronizer  298  along with one of the other four synchronizers  294 ,  295 ,  296  and  297 , respectively. 
     Fourth Embodiment 
     Referring to  FIG. 8 , a multi-speed transmission  300  is depicted. The transmission  300  includes an input member  12  and output member  14 . In this embodiment, the input member  12  and the output member  14  are shafts, and will be referred to as such. Those skilled in the art will appreciate that the input and output members  12 ,  14  may be components other than shafts. The input shaft  12  is continuously connected with an engine (not shown). The output shaft  14  is continuously connected with the final drive unit (not shown). The transmission  300  includes a countershaft gearing arrangement  317  that includes intermediate shafts, a countershaft, co-planar intermeshing gear sets and selectively engagable synchronizers as will be described herein. For instance, the countershaft gearing arrangement  317  includes an intermediate shaft  316  and an intermediate shaft  318 , which is a sleeve shaft concentric with the intermediate shaft  316 . The intermediate shafts  318  and  316  are referred to in the claims as the first and second intermediate shafts, respectively. The countershaft gearing arrangement  317  further includes a countershaft  322 . Countershaft  322  is referred to in the claims as the first countershaft. The countershaft  322  is spaced from and parallel with the input shaft  12 , the output shaft  14  and the intermediate shafts  316 ,  318 . 
     A differential gear set  330 , which is a double-pinion planetary gear set, is connected between the input shaft  12  and the output shaft  14 . The differential gear set  330  includes sun gear member  332  (labeled S) connected for common rotation with the intermediate shaft  316 , a ring gear member  334  (labeled R) and a carrier member  337  connected for common rotation with the intermediate shaft  18 , and which rotatably supports two sets of pinion gears  338 ,  339  (labeled P 1  and P 2 , respectively). Pinion gears  338  intermesh with the sun gear member  332  and with pinion gears  339 . Pinion gears  339  intermesh with the ring gear member  334 . 
     The countershaft gearing arrangement  317  also includes co-planar, intermeshing gear sets  340 ,  350 ,  360 ,  370  and  380 . Gear set  340  includes gears  342  and  344 . Gear  342  is connected for common rotation with the intermediate shaft  318  and intermeshes with gear  344 , which is rotatable about and selectively connectable with the countershaft  322 . 
     Co-planar gear set  350  includes gear  352  and gear  354 . Gear  352  is connected for common rotation with intermediate shaft  318  and intermeshes with gear  354 , which rotates about and is selectively connectable with countershaft  322 . 
     Gear set  360  includes co-planar intermeshing gears  362  and  364 . Gear  362  is connected for common rotation with the intermediate shaft  316  and intermeshes with gear  364 , which is rotatable about and selectively connectable with countershaft  322 . 
     Gear set  370  includes co-planar, intermeshing gears  372  and  374 . Gear  372  rotates about and is selectively connectable with intermediate shaft  316 . Gear  372  intermeshes with gear  374 , which is selectively connectable with countershaft  322 . 
     Gear set  380  includes gear  382  and gear  384 . Gear  382  is connected for common rotation with the output shaft  14  and is selectively connectable with the intermediate shaft  316 . Gear  382  intermeshes with gear  384 . Gear  384  is connected for common rotation with the countershaft  322 . 
     The transmission  300  includes a variety of torque-transmitting mechanisms or devices including input clutch  390 , input clutch  391 , and input clutch  392 . In the claims, input clutch  390  is referred to as the first torque-transmitting mechanism, input clutch  392  is referred to as the second torque-transmitting mechanism and input clutch  391  is referred to as the third torque-transmitting mechanism. Input clutch  390  is selectively engagable to connect the input shaft  12  with the sun gear member  332 . Input clutch  391  is selectively engagable to connect the input shaft  12  with the ring gear member  334 . Input clutch  392  is selectively engagable to connect the input shaft  12  with the sun gear member  332 . The transmission  300  further includes a plurality of selectively engagable synchronizers  393 ,  394 ,  395 ,  396 ,  397 , and  398 . Synchronizer  393  is selectively engagable to connect gear  364  with countershaft  322  for common rotation therewith. Synchronizer  393  is referred to in the claims as the first synchronizer. Synchronizer  394  is selectively engagable to connect gear  354  with countershaft  322  for common rotation therewith. Synchronizer  395  is selectively engagable to connect gear  382 , and therefore output shaft  14 , with intermediate shaft  316  for common rotation therewith. Synchronizer  396  is selectively engagable to connect the gear  344  with the countershaft  322  for common rotation therewith. Synchronizer  397  is selectively engagable to connect gear  374  with countershaft  322  for common rotation therewith. Synchronizer  398  is selectively engagable to ground the ring gear member  334  to the stationary transmission housing  399 . Synchronizer  398  is referred to in the claims as the additional synchronizer. Synchronizer  398  is engaged along with input clutch  392  and synchronizer  393  to provide a reverse torque ratio described with respect to correspondingly numbered components of the transmission  200  of  FIG. 5 . 
     The transmission  300  is capable of transmitting torque from the input shaft  12  to the output shaft  14  in at least seven forward torque ratios and one reverse torque ratio with an engagement schedule as indicated in the truth table of  FIG. 6  with respect to correspondingly-numbered components of the transmission  200  of  FIG. 5 . Up to four additional forward torque ratios (two of which are indicated in  FIG. 6 ) may be achieved for a total of eleven forward torque ratios. 
     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.