I replaced the U Joints on the driveline of my 1975 Corvette. While I was at it, I replaced the 4 speed manual transmission seal on the tailstock. I had trouble getting it seated right. I tried to fabricate a tool out of a piece of wood  with a hole cut out for the shaft, so that I could get more uniform force on the seal. I could not get it seated properly. Does anyone have any idea how to get a new transmission seal in with the transmission still in the car?

There is a seal installer that allows you to tap it in place.   Hopefully someone has one handy.

Make sure you have the right seal, first. Some B/W take the same seal as the 400 automatic, some take a different one.
Also, some seals may have a deeper outer shell than normal, and you can have the seal installed all the way, but it looks like it needs to go in another 1/8" or so to be fully seated, because of it.
It can be a pain to get a seal knocked on in the car, for sure. The seal drivers help, but most of them are so long it's hard to get a good swing at them.
As Ken says, just take your time, and walk it around, a little at a time. I have found that a body hammer with a flat head works best for seal installs...that's the only thing I use if I can't use a seal driver. Adams' Apple2008-08-20 19:05:40