Main Shaft Seal

By Dennis Santopietro

Q: My husband has a 1979 Harley custom chopper w/ a 80 in shovel an 4 speed trans. He’s having problems with the trans. leaking grease on the drive side. The main shaft seal was replaced, was good for a couple weeks then started leaking again. Any ideas?
Anita B via Facebook

A: The bushing that supports the main shaft is probably worn; allowing the main shaft to have excessive runout. New seals will not stop your trans from leaking. The trans will need to be torn down and rebuilt.

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4 Responses to “Main Shaft Seal”

  1. Ed

    It is common on a 4 spd transmission for the mainshaft to be worn .002-.004" where the main drive gear bushing rides on it so when over hauling a 4 spd trans we usually end up replacing the mainshaft as well as the bushing or you will be back in there shortly

  2. Robert

    I have a 2004 H-D Softail FXSTI my speedometer went out I thought so I got one from the dealer installed it and my speedometer is still going all the way up after started. So do I have a bad sensor or am I over looking a fuse some where? Thank You, Robert Coy

  3. Wendell Macklin

    Love your comments

  4. Charles

    The bushing may have moved inward on the shaft.