Smokehouse69

Yesterday one of our new members asked about changing out the leaking shift shaft seal on his TH400. I was just getting ready to tackle that same problem, so today I did it and documented it with pictures. Here we go step by step.
This can be done while the tranny is in the car.
In My Humble Opinion this is 4 on the scale of 1 to 10 in difficulty with tranny filter change a 3.
1. First drain the transmission and remove the pan and unbolt the filter. (No picture necessary here, everyone should know what this messy operation looks like.) :D
After the pan is off, move the shaft through the gears and observe how everything functions. So when you get it back together you can function check it.

2. Then the trickiest part of the whole deal, get the pin out of the bottom of the shaft. It looks like a finishing nail, and if there is a way of getting it out without bending it, I couldn't figure it out. Slide the head of the pin back as far as you can and bend it enough to pull it out. This is really pretty easy to do, getting it back in is the tougher part.

3. With the pin out the castle nut can be taken off the bottom of the shaft. You will have to unscrew the nut and pull up on the shaft at the same time, with the nut off the shaft should move up without too much trouble. The clearance of the shaft and case is pretty tight so you'll have to twist and pull on the shaft from the outside, while pushing from the inside.

4. After the shaft is out the seal is very easy to remove with a small screwdriver or needlenosed pliers. Just pop it out.

5. Clean the shaft opening with brakecleaner or some other light solvent to make sure the area the new seal is going into is clean.

6. The next step is probably unecessary, but I've always done it in the past so I did it this time. I smeared a very, very thin coat of hightemp silicon sealer on the metal edge of the new seal. The set it in the shaft hole making sure it was level.

7. Then I took a 14mm deepsocket (which was very close to the same size in diameter as the seal. With the socket I tapped the seal down into the hole.

8. Then I inspected the shaft and made sure it was smooth and not rusty, I then coated it with ATF and slipped it into the shaft hole and down into the shift pawl.

9. After the threaded end of the shaft is through the pawl, slip the castle nut under the pawl and start threading it onto the shaft. Be careful to line up the shaft and the pawl slot correctly. After the shaft is firmly attached to the pawl, you can start the tough part.

10. Take the bent pin and push it into the hole, using needle nosed pliers I was able to straighten and shove the pin through the hole. Once it was completely through the hole it appeared to be straight and in the groove at the bottom of the shaft.

11. Move the shifter through the gear and make sure everything functions as it did before.

Here is a picture of the pin as I bent it to remove and install it.



Here is a picture of the shaft, with the now bent pin laying in the groove it goes into after it is in place. The castlenut that holds the shaft in place is setting their also.



Here is a picture of the shift pawl and hole the shaft sets in with the shaft out.



Here is a picture of me removing the castlenut from the shaft.



Here is the old seal after I pried it out.



Here is the shaft hole cleaned and ready for the new seal.



Here is the new seal after it was in place.




Then just reverse the operation to put everything back together. I hope this helps some of you guys to fix your leaking seals.

shoptek

Very good info. Thanks for taking the time to document it :cheers:

442olds

There is a tool that slides over the shaft and threads into the seal and then it has a bolt that you tighten down (it pushes on the shaft) and pulls the seal out. Then you slide the new seal on and hammer it back into place with a deep well socket. If I have a digital camera over the weekend I will post a pic of the tool.

Smokehouse69

Thanks for the info, it sure would make this trouble prone seal easier to get out with a special removal tool. Perhaps we could get one into the tool loan program, that way everyone with a leaking seal wouldn't have to buy the tool for a 5 minute job.
By the way welcome to the Forum!

Frank75

Thanks for the documentation. I may have to do this some time.