I picked up a used Th400 and just got around to installing it. I replaced the seals and filter. I had some trouble locating the correct rear tail shaft seal but I found one that fit the opening in the case ( the case appears to require a larger outer diameter. But with this larger diameter outer opening comes a larger inner seal around the shaft and appears to be marginal if it seals at all. I drove it for a few miles maybe ten without to much trouble, it was leaking slightly . I let the car sit for a week or two and Friday when the weather was mid 40's I took the car out for a few more miles of break in. That is when I noticed the huge amount of tranny fluid all over the under side of the car it was all over and getting flung around by the drive shaft . I checked things today and the seal is leaking but I grabbed the drive shaft by the front yoke and wiggled it. Well actually moved it. Question 1. are there different diameter th400 yokes that would require a different seal? I found a th400 seal with a 1.69 diameter yoke seal but the outer diameter was to small. There is a larger diameter outer seal I believe 2.7 inch. but the inside yoke diameter is 1.88 and I think I have this seal and maybe why it is leaking so bad. 2. The other question is should the tail shaft be moving so freely up and down and side to side? I am thinking probably not, and this may indicate that I need to replace the tail shaft bearings. Any usable input on the proper seal or possibly changing the yoke would be appreciated as well as your thoughts on the Tail shaft movement. I would really like to have the car sorted out by spring and if I need a tranny rebuild I need to get moving. Thank you Joe
Maybe the rear bushing is shot? You might ask the previous owner if he liked to do neutral dumps. Does it move more left to right or up and down?
there are different diameter tail housings and different diameter drive shaft yokes. sounds like you have the wrong yoke for that tail housing
The early 400 used about a 1.69" dia yoke, most were about 1.89" You must have the right tailpiece to fit your yoke. Otherwise the inner bearing won't support the shaft/yoke, resulting in quick seal (WHERE DID YOU GET THAT?) failure, and probably more serious stuff soon. You can change the parts with the trans in the car. Bruce Roe
