General Motors installed the 350 Turbo Hydra-Matic three-speed automatic transmission in a number of its models between 1964 and 1972. Since these are vintage vehicles, there's is a good chance the transmission seals could fail. The rear seal on a Turbo Hydra-Matic is located where the drive shaft meets the rear of the transmission, and serves to hold the transmission fluid inside. Replacement of the rear seal is a fairly difficult task, but can be accomplished by most do-it-yourself mechanics in about an hour using basic repair tools.
Raise the vehicle on a hydraulic lift. Drain the transmission. Remove the two bolts holding the carrier bearing to the cross member and remove the bearing. The carrier bearing is located in the middle of the drive shaft. There is one bolt on either side of it.
Use a hammer and pin punch to drive the roll pin out of the output flange. The output flange is located at the rear of the transmission and is usually painted black.
Pull the drive shaft rearward off of the transmission output shaft and fasten the drive shaft out of the way.
Pry the old seal out of its seat using a seal puller or long screwdriver. With the drive shaft removed, the seal should be immediately apparent on the back face of the transmission.
Position the new seal and place a seal driver or socket over the seal and tap the seal into place.
Perform Steps One through Three in reverse order to reinstall the drive line components.
Fill the transmission with nine quarts of new transmission fluid. Pour the transmission fluid in through the dipstick tube.
