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These pages will hopefully provide the reader with a brief overview of transmission options for RWD Mopars. While the focus is on A-body applications, some technical notes, such as transmission identication, transcend platform discussions and can hopefully provide useful information to all Mopar hobbiests. Before spliting into discussions of automatic or manual transmissions, the commonalities of the two should be covered briefly.
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Not all Mopar transmissions are the same length. Excluding 4WD truck and some van "shorty" transmissions, the world of Chrysler passenger car transmissions can be divided into the ranks of "long tailshaft" and "short tailshaft" transmissions. Automatics are simple, A-727s are long tailshaft and A-904s are short tailshaft. For manual transmissions, some further defining is required. All A-body and F-body manual transmissions are short tailshaft transmissions. All B-body, C-body, and E-body transmissions are long tailshaft transmissions.
In addition to a length issue, for each of the three families of engines Chrysler produced, there were three seperate bellhousing bolt patterns. G/RG family engines (170/198/255 slant sixes) used one pattern, A/LA engines (273/318/340/360 small blocks) used another pattern, and B/RB engines (361/383/400/413/426/440) used yet another. Some truck bellhousings were built to accept multiple engine applications, but for the most part Chrysler built different bellhousings for different engines.
This is another very important aspect to transmissions, specifically the flywheel or flexplate, that must be discussed. In 1968, slant six and small block engines began using a larger counterbore in the crankshaft and a larger torque converter snout. The newer diameter is 1/4" larger. 1968 & later torque converters can not be used with 1967 & earlier cranks for this reason. The opposite scenario, a 1968 and later crank with a 1967 & earlier torque converter, is possible, however, an adapter ring must be fitted to the counterbore on the later crank so that the converter snout fits snuggly in the counterbore.
The flex plate center register was larger on 1968 & later units as well. When swapping transmissions, the flex plate should match the crank (if its a 68 & later crank, use a 68 & later flexplate!). The same applies to flywheels! 1967 and earlier flywheels had a smaller center hole than 1968 and later flywheels.
The size that was adapted is the same size that the B/RB motors adopted in 1962. There was also a change to the bolt pattern on G/RG engines.
Early models of the A-727 and A-904 transmissions used a fine spline input shaft, later models used a course spline input shaft. since the input shaft's spline engages the torque converter, the torque converter must match the input shaft. In other words, you can use a 1964 torque converter on a 1970 transmission. The change over years were different the A-727 and the A-904. In 1966, The A-727 adopted the course spline input shaft (along with adopting a lever shift gear selector in place of the 1965 and earlier cable shift gear selector). In 1968, the A-904 adopted the course spline input shaft (along with the core-bore change discussed earlier).
There are detailed pictures of the A-727 at Allpar's Torqueflite page.
For many year mopars, crossmembers varied from automatics to four speeds.