The Hydra-Matic transmission needed an additional crossmember and rear mount, but the 3-speed and much heavier S420 4-speed no longer needed a rear transmission mount/cross-member.
The Hydramatic transmission length is 8" inches longer and its torque tube is 8" inches shorter.
More weight is hanging farther out pass the flywheel housing.
Hence the need for the a rear transmissions tail housing cross-member.
Picture: 1954 Chevrolet 1/2 ton H-M rear tail housing crossmember The re-engineering of the cross-member under the flywheel housing in 1954 eliminated the need
for a rear transmissions tail housing cross-member on the 3 and 4 speed transmissions.
Picture: 1954 Chevrolet 1/2 ton rear of 4 speed trans. Both 3 and 4 speed transmission are the same length so are the length of their torque tubes.
TT Measurements There was a company that made some kind of support
Picture 1 ,
Picture 2,
Picture 3,
Picture 4 that clamped around the tail of the U-Joint ball housing and the torque tube.
Its soul purpose was to prevent the torque tube from drooping downward.
The reason for the torque tube droop is probably coming from the downward force when applying the brakes.
Picture 5 Here is a
GM film Strip (Starts on picture 35), about repairing the ball housing and the end of the torque tube.
Because of down force wearing them out.
