Expert: Brad Sears - 6/2/2008

Question
I have a 1966 Mustang with a 6 cylinder, 3-speed manual transmission.  I have a fluid leak out the back of the transmission where the drive shaft attaches to the transmission and wanted to know the process to replace the seal.

Answer
The rear seal can be replaced by removing the driveshaft. Disconnect the rear universal joint from the rear end flange. Then slide the drive shaft towards the rear of the car and it will pull off the spline on the back of the transmission. They make a special puller to use with a sliding hammer puller to get the seal out of the transmission tail housing. If you are real carefully you can use a chisel and hammer. Use the chisel as a bit of a lever holding it on an angle with the point on the exposed edge of the seal and pointing towards the back of the car. Tap the end of the chisel a few taps and then go around the seal. To install the new seal you will need a tool or a piece of pipe that will fit the seal and allow you to tap the seal into place even all around. While the drive shaft is out you will want to check the seal area on the drive shaft to make sure that it is not worn. There is also a sleeve bearing inside the tail housing that when worn will destroy then new seal if it is worn. To check this grab the front U joint area before removing the drive shaft. If you can move it up and down the bearing is worn. It take a special tool to remove and replace it.
Brad