TH350 - are there good years and how compatible are they between BOP, cad, chevy

[AuroraGirl]

I got the go ahead from my gma to clean up and sell off the old relics(40s dodge, 75 pontiac, 79/80 oldsmobile, some 40s/50s chevy/gmc trucks, some old ford model a/t, etc) and my 75 pontiac, 79 and 80 olds all have a TH350. I also have two TH350s sitting in a shed, I also have a TH350 on my 78 chevy frame, and I also have a TH350 in my 77 Buick.

So, I have a lot of TH350. I plan on pulling the engines so I have a small block pontiac and 2 small block olds on hand, but wondering if I should keep the trans for parts/rebuild for any future, or if they would bolt up to any of my others or if thee would be compatbility issues. Obviously, they have all been sitting for years and would likely need work, but hey maybe I can learn how to rebuild a trans? Plenty of practice material haha.

 

[Ricko1966]

Plenty of compatibility issues. TH 350 2wd has three different tailshaft lengths.6inch 9inch and 12inch. B.O.P has different bellhousing bolt pattern than chevy and some have both patterns. I think it was 1980 they changed to TH350 c. Which uses a lockup converter and that converter cannot be used in regular TH350

 

[Matt69olds]

There are lots of little differences. The early sunshells are thicker than the later parts. The later parts use bearings instead of thrust washers. Some shifter linkages use a “S” shaped link between the manual valve and rooster comb, others used a link shaped more like a “Z”. Most components will interchange as an assembly, but mixing parts can create headaches.

Ron Sessions published a book years ago that covered production changes and interchange, it’s out of print but I find it occasionally at swap meets.