Abstract:
A multiple shift fork, single shift rail assembly reduces weight and complexity in manual and dual clutch transmissions. In a first embodiment, a stationary shift rail includes pluralities of detenting recesses and cooperating detent assemblies are mounted on the shift forks. Associated actuators translate the shift forks and synchronizer clutches. In a second embodiment, the detenting recesses reside on the outside surface of the shift forks and the detent assemblies are mounted in the transmission housing. In a third embodiment, one shift fork is slidably mounted on the shift rail and includes an external detent assembly. The shift rail itself translates and includes detenting recesses and a second shift fork connected thereto.

Description:
FIELD 
       [0001]    The present disclosure relates to shift assemblies for vehicular transmissions and more particularly to a shift assembly for manual or dual clutch vehicular transmissions having at least two shift forks disposed on a single shift rail. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    Gear changes in manual and dual clutch transmissions are generally achieved by a synchronizer clutch which is splined to and which rotates with an associated shaft. Adjacent the synchronizer clutch is one or a pair of gears which provide distinct gear or speed ratios. Axial motion of the synchronizer clutch first synchronizes and then couples the gear to the shaft and drive torque is then applied to the engaged gear or shaft. 
         [0004]    Axial motion of the synchronizer clutch is commanded by a shift fork which engages a groove in the periphery of the clutch and which is slidably disposed on a shift rail. A linear output of a two or three position actuator may be directly connected to the shift fork or the shift fork may be secured to the shift rail, in which case the actuator is connected to and translates the shift rail. 
         [0005]    Especially in the latter configuration, each shift fork requires a dedicated shift rail. Thus, in a five speed transmission which encompasses six gears with reverse, it is necessary to have at least three shift rails, actuators and shift forks. In a six or seven speed transmission (which encompasses seven or eight speeds when reverse is included), it is necessary to have at least four shift rails, actuators and shift forks. 
         [0006]    Because each shift rail occupies space in the transmission and requires mounting bosses and/or linear bearings, they add to the complexity and cost of a transmission. Reducing their number is thus desirable. 
       SUMMARY 
       [0007]    The present invention provides several embodiments of a multiple shift fork, single shift rail assembly. In a first embodiment, a stationary shift rail includes pluralities of detenting recesses and cooperating detent assemblies are mounted on the shift forks. Associated actuators translate the shift forks and synchronizer clutches. In a second embodiment, the detenting recesses reside on the outside surface of the shift forks and the detent assemblies are mounted in the transmission housing. In a third embodiment, one shift fork is slidably mounted on the shift rail and includes an external detent assembly. The shift rail itself translates and includes detenting recesses and a second shift fork connected thereto. In every embodiment, more than two shift forks may be associated with a single shift rail if desired. 
         [0008]    Thus it is an object of the present invention to provide a single shift rail for a transmission having two shift forks disposed thereon. 
         [0009]    It is a further object of the present invention to provide a single shift rail for a manual or a dual clutch transmission having two shift forks disposed thereon. 
         [0010]    It is a still further object of the present invention to provide a stationary shift rail having detenting recesses and shift forks carrying detent assemblies. 
         [0011]    It is a still further object of the present invention to provide a stationary shift rail which receives two shift fork having detenting recesses on their exterior surfaces. 
         [0012]    It is a still further object of the present invention to provide an axially translating shift rail having detenting recesses and a first shift fork secured thereto and a second shift fork slidable thereon with detenting recesses on its exterior surface. 
         [0013]    It is a still further object of the present invention to provide a single shift rail having more than two shift forks disposed thereon. 
         [0014]    Further objects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0015]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0016]      FIG. 1  is diagrammatic, side elevational view in partial section of a portion of a transmission incorporating a first embodiment of a single shift rail assembly according to the present invention; 
           [0017]      FIG. 2  is a perspective view of a first embodiment of a single shift rail assembly according to the present invention; 
           [0018]      FIG. 3  is diagrammatic, side elevational view in partial section of a portion of a transmission incorporating a second embodiment of a single shift rail assembly according to the present invention; 
           [0019]      FIG. 4  is a perspective view of a second embodiment of a single shift rail assembly according to the present invention; 
           [0020]      FIG. 5  is diagrammatic, side elevational view in partial section of a portion of a transmission incorporating a third embodiment of a single shift rail assembly according to the present invention; and 
           [0021]      FIG. 6  is a perspective view of a third embodiment of a single shift rail assembly according to the present invention 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0023]    With reference now to  FIG. 1 , a portion of a vehicular transmission is illustrated and generally designated by the reference number  10 . The transmission  10  may be either a manual transmission, a dual clutch transmission (DCT) or other configuration wherein synchronizers and face or dog clutches are utilized to connect a plurality of gears to one or more associated shafts. The transmission  10  includes an exterior housing  12  which typically includes openings, counterbores, shoulders, flanges and the like which locate, receive and retain various components of the transmission  10 . 
         [0024]    Supported for rotation within the housing  12  on, for example pairs of ball or tapered roller bearing assemblies  14  are various shafts, one of which, a countershaft or layshaft  16 , is illustrated. The countershaft  16  freely rotatably receives a plurality of spur or preferably helical gears  22 ,  24 ,  26  and  28 . The gears  22 ,  24 ,  26  and  28  are paired and in constant mesh with adjacent gears (not illustrated) on one or more adjacent parallel shafts and together these pairs of gears provide a selection of forward (and reverse) speeds or gear ratios. 
         [0025]    Between the adjacent gears  22  and  24  is disposed a first synchronizer clutch  30 . The first synchronizer clutch  30  includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The first synchronizer clutch  30  is rotationally connected to the countershaft  16  by a first interengaging male and female spline set  32  but is free to axially translate therealong. When the first synchronizer clutch  30  is translated to the left or right on the countershaft  16 , it exclusively first synchronizes and then positively couples the gear  22  or the gear  24  to the countershaft  16 . The first synchronizer clutch  30  includes a circumferential channel or groove  34 . 
         [0026]    Between the adjacent gears  26  and  28  is disposed a second synchronizer clutch  40 . The second synchronizer clutch  40  also includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The second synchronizer clutch  40  is rotationally connected to the countershaft  16  by a second interengaging male and female spline set  42  but is free to axially translate therealong. When the second synchronizer clutch  40  is translated to the left or right on the countershaft  16 , it exclusively first synchronizes and then positively couples the gear  26  or the gear  28  to the countershaft  16 . The first synchronizer clutch  30  also includes a circumferential channel or groove  44 . 
         [0027]    Referring now to  FIGS. 1 and 2 , secured within suitable blind openings or bores  48  in the housing  12  is a stationary shift rail  50 . The shift rail  50  is preferably a round shaft and may be hollow to reduce its weight. The stationary shift rail  50  is spaced from and parallel to the countershaft  16 . The stationary shift rail  50  defines a first set of detenting recesses  52 A,  52 B and  52 C and a second set of detenting recesses  54 A,  54 B and  54 C which are spaced from the first set of recesses  52 A,  52 B and  52 C. 
         [0028]    Received for bi-directional axial translation on the stationary shift rail  50  are a first shift fork assembly  60  and a second shift fork assembly  80 . The first shift fork assembly  60  includes a first cylindrical or tubular body  62  defining a through passageway  64  that receives the stationary shift rail  50 . A first pair of linear ball bearing assemblies  66  disposed within the passageway  64  and generally proximate the ends of the tubular body  62  reduce friction and stabilize the first shift fork assembly  60  on the stationary shift rail  50 . A first shift fork  68  extends radially from the cylindrical body  62  and includes a first yoke  70  which engages the circumferential channel or groove  34  in the first synchronizer clutch  30 . 
         [0029]    The first cylindrical body  62  also includes a first radially oriented housing  72  which receives a first detent ball  74  which is biased toward the stationary shift rail  50  and the first set of detenting recesses  52 A,  52 B and  52 C by a first compression spring  76 . The output of a first bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  78  is coupled to a first arm or extension  79  of the first cylindrical body  62  of the first shift fork assembly  60  and translates from a center, neutral position illustrated in  FIG. 1  to a first active position to the left to cause synchronization and engagement of the first gear  22  or to a second active position the right to cause synchronization and engagement of the second gear  24 . 
         [0030]    When the first shift fork assembly  60  is in the left, first active position, the detent ball  74  is in the first detenting recess  52 A and cooperation between the first recess  52 A and the detent ball  74  resists motion of the first shift fork assembly  60 . When the first shift fork assembly  60  is in the center, neutral position, the detent ball  74  is in the second detenting recess  52 B and cooperation between the second recess  52 B and the detent ball  74  again resists motion of the first shift fork assembly  60 . When the first shift fork assembly  60  is in the right, second active position, the detent ball  74  is in the third detenting recess  52 C and cooperation between the third recess  52 C and the detent ball  74  once again resists motion of the first shift fork assembly  60 . 
         [0031]    The second shift fork assembly  80  also includes a second cylindrical or tubular body  82  defining a through passageway  84  that receives the stationary shift rail  50 . A second pair of linear ball bearing assemblies  86  disposed generally proximate the ends of the second tubular body  82  reduce friction and stabilize the second shift fork assembly  80  on the stationary shift rail  50 . A second shift fork  88  extends radially from the second cylindrical body  82  and includes a second yoke  90  which engages the circumferential channel or groove  34  in the second synchronizer clutch  40 . 
         [0032]    The second cylindrical body  82  also includes a radially oriented second housing  92  which receives a second detent ball  94  which is biased toward the stationary shift rail  50  and the second set of detenting recesses  54 A,  54 B and  54 C by a second compression spring  96 . The output of a second bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  98  is coupled by a second arm or extension  99  to the second cylindrical body  82  of the second shift fork assembly  80  and translates from a center, neutral position illustrated in  FIG. 1  to a first active position to the left to cause synchronization and engagement of the third gear  26  or to a second active position the right to cause synchronization and engagement of the fourth gear  28 . 
         [0033]    When the second shift fork assembly  80  is in the left, first active position, the second detent ball  94  is in the first detenting recess  54 A and cooperation between the first recess  54 A and the detent ball  94  resists motion of the second shift fork assembly  80 . When the second shift fork assembly  80  is in the center, neutral position, the second detent ball  94  is in the second detenting recess  54 B and cooperation between the second recess  54 B and the detent ball  94  again resists motion of the second shift fork assembly  80 . When the second shift fork assembly  80  is in the right, second active position, the second detent ball  94  is in the third detenting recess  54 C and cooperation between the third recess  54 C and the detent ball  94  once again resists motion of the second shift fork assembly  80 . 
         [0034]    Referring now to  FIGS. 3 and 4 , a second embodiment of a single shift rail assembly according to the present invention is illustrated and generally designated by the reference number  100 .  FIG. 3  includes a portion of a vehicular transmission  110 . As above, the transmission  110  may be either a manual transmission, a dual clutch transmission (DCT) or other configuration wherein synchronizers and face or dog clutches are utilized to connect a plurality of gears to one or more associated shafts. The transmission  110  includes an exterior housing  112  which receives and supports, among other components, pairs of ball or tapered roller bearing assemblies  114  which, in turn, rotatably support a countershaft or layshaft  116 . The countershaft  116  freely rotatably receives a plurality of spur or preferably helical gears  122 ,  124 ,  126  and  128 . The gears  122 ,  124 ,  126  and  128  are paired and in constant mesh with adjacent gears (not illustrated) on one or more adjacent parallel shafts and together these pairs of gears provide a selection of forward (and reverse) speeds or gear ratios. 
         [0035]    Between the adjacent gears  122  and  124  is disposed a first synchronizer clutch  130 . The first synchronizer clutch  130  includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The first synchronizer clutch  130  is rotationally connected to the countershaft  116  by a first interengaging male and female spline set  132  but is free to axially translate therealong. When the first synchronizer clutch  130  is translated to the left or right on the countershaft  116 , it exclusively first synchronizes and then positively couples the gear  122  or the gear  124  to the countershaft  116 . The first synchronizer clutch  130  includes a circumferential channel or groove  134 . 
         [0036]    Between the adjacent gears  126  and  128  is disposed a second synchronizer clutch  140 . The second synchronizer clutch  140  also includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The second synchronizer clutch  140  is rotationally connected to the countershaft  116  by a second interengaging male and female spline set  142  but is free to axially translate therealong. When the second synchronizer clutch  140  is translated to the left or right on the countershaft  116 , it exclusively first synchronizes and then positively couples the gear  126  or the gear  128  to the countershaft  116 . The second synchronizer clutch  140  also includes a circumferential channel or groove  144 . 
         [0037]    Secured within suitable blind openings or bores  148  in the housing  112  is a stationary shift rail  150 . The stationary shift rail  150  is spaced from and parallel to the countershaft  116 . Disposed in general radial alignment with the first synchronizer clutch  130  for bi-directional translation on the stationary shift rail  150  is a first shift fork assembly  160  and in general radial alignment with the second synchronizer clutch  140  for bi-directional translation on the stationary shift rail  150  is a second shift fork assembly  190 . 
         [0038]    The first shift fork assembly  160  includes a first, relatively short cylindrical or tubular body  162  defining a through passageway  164  that receives the stationary shift rail  150 . A first pair of linear ball bearing assemblies  166  disposed within the passageway  164  generally occupy the length of the tubular body  162 , reduce friction and stabilize the first shift fork assembly  160  on the stationary shift rail  150 . A first shift fork  168  extends radially from the cylindrical body  162  and includes a first yoke  170  which engages the circumferential channel or groove  134  in the first synchronizer clutch  130 . 
         [0039]    The first cylindrical body  162  also includes a first set of detenting recesses  172 A,  172 B and  172 C. The first set of detenting recesses  172 A,  172 B and  172 C are circumferentially and radially aligned with a first detenting assembly  174  which includes a detent ball  176  received within a cylindrical housing  178  which extends from and is secured to the housing  112 . A compression spring  182  biases the detent ball  176  toward the recesses  172 A,  172 B and  172 C. The cylindrical or tubular body  162  includes an arm or extension  184  that is coupled to the output of a first bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  186 . The output of the actuator or operator  186  translates from a center, neutral position illustrated in  FIG. 3  to a first active position to the left to cause synchronization and engagement of the first gear  122  or to a second active position the right to cause synchronization and engagement of the second gear  124 . 
         [0040]    When the first shift fork assembly  160  is in the left, first active position, the detent ball  176  is in the third detenting recess  172 C and the first detenting assembly  174  resists motion of the first shift fork assembly  160 . When the first shift fork assembly  160  is in the center, neutral position, the detent ball  176  is in the second detenting recess  172 B and the first detenting assembly  174  again resists motion of the first shift fork assembly  160 . When the first shift fork assembly  160  is in the right, second active position, the detent ball  176  is in the first detenting recess  172 A and the first detenting assembly  174  once again resists motion of the first shift fork assembly  160 . 
         [0041]    The second shift fork assembly  190  includes a second, relatively short cylindrical or tubular body  192  defining a through passageway  194  that receives the stationary shift rail  150 . A second pair of linear ball bearing assemblies  196  disposed within the passageway  194  generally occupy the length of the tubular body  192 , reduce friction and stabilize the second shift fork assembly  190  on the stationary shift rail  150 . A second shift fork  198  extends radially from the second cylindrical body  192  and includes a second yoke  200  which engages the circumferential channel or groove  144  in the second synchronizer clutch  140 . 
         [0042]    The second cylindrical body  192  also includes a second set of detenting recesses  202 A,  202 B and  202 C. The second set of detenting recesses  202 A,  202 B and  202 C are circumferentially and radially aligned with a second detenting assembly  204  which includes a detent ball  206  received within a cylindrical housing  208  which extends from and is secured to the housing  112 . A second compression spring  212  biases the detent ball  206  toward the second set of recesses  202 A,  202 B and  202 C. The cylindrical or tubular body  192  includes an arm or extension  214  that is coupled to the output of a second bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  216 . The output of the actuator or operator  216  translates from a center, neutral position illustrated in  FIG. 3  to a first active position to the left to cause synchronization and engagement of the third gear  126  or to a second active position the right to cause synchronization and engagement of the fourth gear  128 . 
         [0043]    When the second shift fork assembly  190  is in the left, first active position, the detent ball  206  is in the third detenting recess  202 C and the second detenting assembly  204  resists motion of the second shift fork assembly  190 . When the second shift fork assembly  190  is in the center, neutral position, the detent ball  206  is in the second detenting recess  202 B and the second detenting assembly  204  again resists motion of the second shift fork assembly  190 . When the second shift fork assembly  190  is in the right, second active position, the detent ball  206  is in the first detenting recess  202 A and the second detenting assembly  204  once again resists motion of the second shift fork assembly  190 . 
         [0044]    Referring now to  FIGS. 5 and 6 , a third embodiment of a single shift rail assembly according to the present invention is illustrated and generally designated by the reference number  300 .  FIG. 5  includes a portion of a vehicular transmission  310 . Once again, the transmission  310  may be either a manual transmission, a dual clutch transmission (DCT) or other configuration wherein synchronizers and face or dog clutches are utilized to connect a plurality of gears to one or more associated shafts. The transmission  310  includes an exterior housing  312  which receives and supports, among other components, pairs of ball or tapered roller bearing assemblies  314  which, in turn, rotatably support a countershaft or layshaft  316 . The countershaft  316  freely rotatably receives a plurality of spur or preferably helical gears  322 ,  324 ,  326  and  328 . The gears  322 ,  324 ,  326  and  328  are paired and in constant mesh with adjacent gears (not illustrated) on one or more adjacent parallel shafts and together these pairs of gears provide a selection of forward (and reverse) speeds or gear ratios. 
         [0045]    Between the adjacent gears  322  and  324  is disposed a first synchronizer clutch  330 . The first synchronizer clutch  330  includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The first synchronizer clutch  330  is rotationally connected to the countershaft  316  by a first interengaging male and female spline set  332  but is free to axially translate therealong. When the first synchronizer clutch  330  is translated to the left or right on the countershaft  316 , it exclusively first synchronizes and then positively couples the gear  322  or the gear  324  to the countershaft  316 . The first synchronizer clutch  330  includes a circumferential channel or groove  334 . 
         [0046]    Between the adjacent gears  326  and  328  is disposed a second synchronizer clutch  340 . The second synchronizer clutch  340  also includes both a pair of synchronizer assemblies and a pair of face or dog clutches. The second synchronizer clutch  340  is rotationally connected to the countershaft  316  by a second interengaging male and female spline set  342  but is free to axially translate therealong. When the second synchronizer clutch  340  is translated to the left or right on the countershaft  316 , it exclusively first synchronizes and then positively couples the gear  326  or the gear  328  to the countershaft  316 . The second synchronizer clutch  340  also includes a circumferential channel or groove  344 . 
         [0047]    Secured within an aligned, opposed pair of mounting openings or bores  346  in the housing  312  are a respective pair of linear ball bearing assemblies  348  which slidably and rotatably receive a single shift rail  350 . Axial translation of the single shift rail  350  is, however, limited by the adjacent walls of the housing  312  and rotation is inhibited by components attached to the shift rail  350 . The shift rail  350  is spaced from and parallel to the countershaft  316 . Disposed in general radial alignment with the first synchronizer clutch  330  for bi-directional translation on the single shift rail  350  is a first shift fork assembly  360  and in general radial alignment with the second synchronizer clutch  340  for bi-directional translation with the single shift rail  350  is a second shift fork assembly  390 . 
         [0048]    The first shift fork assembly  360  includes a first, relatively long cylindrical or tubular body  362  defining a through passageway  364  that receives the single shift rail  350 . A pair of linear ball bearing assemblies  366  disposed proximate the ends of the passageway  364  reduce friction and stabilize the first shift fork assembly  360  on the stationary shift rail  350 . A first shift fork  368  extends radially from the cylindrical body  362  and includes a first yoke  370  which engages the circumferential channel or groove  334  in the first synchronizer clutch  330 . 
         [0049]    The first cylindrical body  362  also includes a first set of detenting recesses  372 A,  372 B and  372 C. The first set of detenting recesses  372 A,  372 B and  372 C are circumferentially and radially aligned with a first detenting assembly  374  which includes a detent ball  376  received within a cylindrical housing  378  which extends from and is secured to the housing  312 . A compression spring  382  biases the detent ball  376  toward the recesses  372 A,  372 B and  372 C. The cylindrical or tubular body  362  includes an arm or extension  384  that is coupled to the output of a first bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  386 . The output of the first actuator or operator  386  translates the first shift fork assembly  360  from a center, neutral position illustrated in  FIG. 5  to a first active position to the left to cause synchronization and engagement of the first gear  322  or to a second active position the right to cause synchronization and engagement of the second gear  324 . 
         [0050]    When the first shift fork assembly  360  is in the left, first active position, the detent ball  376  is in the third detenting recess  372 C and the first detenting assembly  374  resists motion of the first shift fork assembly  360 . When the first shift fork assembly  360  is in the center, neutral position, the detent ball  376  is in the second detenting recess  372 B and the first detenting assembly  374  again resists motion of the first shift fork assembly  360 . When the first shift fork assembly  360  is in the right, second active position, the detent ball  376  is in the first detenting recess  372 A and the first detenting assembly  374  once again resists motion of the first shift fork assembly  360 . 
         [0051]    The second shift fork assembly  390  includes a second, relatively short cylindrical or tubular body  392  defining a through passageway  394  that receives the single shift rail  350 . The second cylindrical or tubular body  392  is secured to the single shift rail  350  by any suitable fastener such as a set screw  396 , a taper pin or an interference fit. A second shift fork  398  extends radially from the second cylindrical body  392  and includes a second yoke  400  which engages the circumferential channel or groove  344  in the second synchronizer clutch  340 . The second cylindrical or tubular body  392  also includes an arm or extension  404  that is coupled to the output of a second bi-directionally translating, three position electric, pneumatic or hydraulic actuator or operator  406 . The output of the second actuator or operator  406  translates the second shift fork  398  from a center, neutral position illustrated in  FIG. 5  to a first active position to the left to cause synchronization and engagement of the third gear  326  or to a second active position the right to cause synchronization and engagement of the fourth gear  328 . 
         [0052]    Disposed adjacent the first detenting assembly  374  is a second detenting assembly  414 . The second detenting assembly  414  includes a second detent ball  416  received within a cylindrical housing  418  which extends from and is secured to the housing  312 . The cylindrical housing  418  is aligned with the single shift rail  350 . A compression spring  420  biases the detent ball  416  toward a plurality of detenting recesses  422 A,  422 B and  422 C in the single shift rail  350 . 
         [0053]    When the second shift fork assembly  390  is in the left, first active position, the second detent ball  416  is in the third detenting recess  422 C and the second detenting assembly  414  resists motion of the single shift rail  350  and the second shift fork assembly  390 . When the second shift fork assembly  390  is in the center, neutral position, the detent ball  416  is in the second detenting recess  422 B and the second detenting assembly  414  again resists motion of the shift rail  350  and the second shift fork assembly  390 . When the second shift fork assembly  390  is in the right, second active position, the detent ball  416  is in the first detenting recess  422 A and the second detenting assembly  414  once again resists motion of the shift rail  350  and the second shift fork assembly  390 . 
         [0054]    It will be appreciated that, first of all, the relatively long and the relatively short shift fork bodies, e.g.  362  and  162 , of the various embodiments may be arranged and exchanged on the single shift rails  50 ,  150  and  350  as desired and, second of all, use of the relatively short shift fork bodies may readily permit the disposition of three shift fork bodies on either the stationary shift rail  50  of the first embodiment or the sliding shift rail  350  of the third embodiment. 
         [0055]    It will also be appreciated that typically two of the single shift rail assemblies disclosed and claimed herein will be utilized with any given transmission. This configuration represents a reduction in at least one and possibly two shift rails as well as a reduction in the number of mounting features necessarily required to support such shift rails. 
         [0056]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.