It looks like the rear seal on the tail shaft of me TH400 tranny is leaking. It's not a big leak, but it is some thing that needs to be addressed.

Any advice on how to go about knocking this out? I have never done one of these before.

It's not hard. The driveshaft has to come out of course. Carefully pry the seal out with a large screwdriver. Carefully tap in the new one with a plastic hammer or use a small block of wood. Install the driveshaft and you're done. Might leak a little tranny fluid out.

Rob, if its not one thing its another! :) If it is weeping on the outside, a little (just a very thin coat) of RTV on the outside of the new seal might help. If it is on the inside, did the yoke get polished?

Rob, if its not one thing its another! :) If it is weeping on the outside, a little (just a very thin coat) of RTV on the outside of the new seal might help. If it is on the inside, did the yoke get polished?

Kevin - I had the yoke sand blasted and then it was cleaned up pretty good before installing it. I never actually had it physically sent out and polished though.

It's a little more then weeping. It's more like a small drip. But brother, you said it ... It's always something!

Take a look wgere its leaking. As said, if it is leaking from the seal, the OD of the yoke, then yes, polish the slip portion of the yoke and install a new seal.

If the yoke is leaking from the center, the vent hole of the yoke, then the trans should have the O-ring replaced. I have yet to find this O-ring, I'll let the trans guys answer this one. Otherwise, fill the outside of the yoke, where the vent hole is located, with JB Weld, let cure overnight, and re-install.

If you had the yoke sandblasted, polish the slip portion of the yoke. This OD surfasce where the seal rubs against should be smooth, or the irregular surface will tear up the seal.