I am having a problem with my suburban TH400 tranny it is leaking fluid out the tailshaft I have replaced the rear seal and the yoke at the same time but it still it is leaking. Any Ideas the trans is also leaking from the pan but not bad the main leak is on the rear seal.

 

did you put the DS yoke back in the tail houseing dry? if you did there is a good chance you burnt up the new seal before AFT could work it's way on to the soft part of the seal. are you sure it's leaking from the seal?

 

According to the book I have by Ron Sessions "How to work with and modify the turbo hydra-matic 400 transmission"

1). Make sure the leak is really from the rear seal and not somewhere else as airflow under the car will cause fluid to be all over.

2.) Coat new seal OD with nonhardening sealer.....

3.) Coat new seal ID with light grease or petroleum jelly....

4.) Insert new seal with plastic hammer or wood

5.) Polish yoke with 600 grit paper

It's a great book on T400's. All the info on the book is on my page and is sold at most larger book stores.

Miles

 

How about the yoke seal? Look and see if oil is coming out of the small hole ni the backside of the yoke. If you have this hole then you also should have a rubber o-ring on the output shaft.

 

you can watch the oil drain out of the seal when the truck is parked at an incline with the front higher than the rear. The seal seemed a little loose on the yoke. I didn't lube the shaft of the yoke when I installed it. That is probably what the problem was.

Thanks guys!

 

While you are at it replace the extension housing bushing. If possible replace it with a wider one. This would account for the extra clearence.