TH-400 help
 

What do I have- it appears to be a BOP TH-400, but the output yoke is bolted in... what gives?
Can a regular slip yoke be used?

403 Olds, but yes, you can use a slip yoke. There are some specifics that elude me, but the one you need doesn't have splines running the entire length (because the truck output shaft uses an o-ring)

OPH knows, I'm pretty sure it was his posts I gleaned that info from :D

Truck TH400. Yes you can remove the bolt & Yoke then use a sealed slippy Yoke.

Ok, thanks for the info... By sealed, you are referring to a standard TH-400 yoke, yes?

I'm curious ... what was the reason for having it bolt on? I assume there was some sort of sliding shaft downstream?

I guess it's a "truck" model- maybe a GMC product w/ an Olds 403- that GM decided to bolt the yoke in place and have a slip section in the driveshaft...

Yep. A 70s crew cab needed almost nine(!) feet worth of driveshaft. So they used two driveshafts, with a crossmember mounted steady bearing and a slip yoke in the middle. Well, closer to the front, but you get the idea...

It may have been form a late 1970's diesel truck

Jaguar TH400's had a bolt in yoke with round flange.

Me, too.

If you use the O-ring seal on the output shaft having an O-ring groove, you need a vented yoke or the yoke will create vacuum as it pulls out of the trans and bind-up.

If you don't use the O-ring, the vented yoke will piddle trans fluid. Gotta have a sealed yoke, and an output shaft with a missing spline. The missing spline becomes the vent for the yoke, but it vents internal to the trans, so no fluid loss.

So I think those are your two choices: Either you have an O-ring on the output shaft and a vented yoke; or you have a missing spline on the output shaft, and a non-vented yoke.

I don't know how the bolted-yoke output shaft is set up.

I've got a couple of TH400's here in the shop with a bolt on yoke. The are Chevy truck cores. I've seen a few others over the years but can't remember if any were BOP, I was thinking all the ones with a bolt on yoke I've done had Chevy cases.........Cliff

Probably Olds diesel in a GMC like stated earlier. I always put the shaft in a lathe and cut down the o-ring bulkhead so a regular yoke works.