Anyone running a 350C?


New Member
Feb 7, 2002
I am working on a 3.8 transplant into an 81 TTA, and I was wondering about the transmission that's in there. It is a 350C and has a lockup torque convertor. I'd like to save money where I can on this, and I like the driveability of the car with the lockup. I hope to get the car into the high 11's to start. Is it worth beefing this tranny up, or should I go a more conventional route? Also, can a GN ECM get this thing to lockup or will I have to do it manually? Any help would be appreciated.

You should be able to use the TH350C with a N/A 3.8, but since
the TH350C uses a vacuum modulator, a boosted 3.8 will pose
a few problems that I am not experienced in dealing with. The
older TH350C's used a two conductor plug for the lockup. If you are going to replace the complete harness with a later
harness, you will have to replace the 4-prong plug in the case
with one from a later transmission. Your local transmission shop
should stock new ones.
That's a good point about the modulator, I forgot all about that thing (hard to believe because it went out twice while I was driving the car). The thing is, it is in a turbo car - the TA has a turbo 301, so i guess I'll have to dig into the plumbing and see how GM did it. Thanks for the info.
Just make sure the modulator doesn't receive boost and you should be ok. The modulator valve moves inward when the vacuum signal goes to 0 and returns outward to the modulator when vacuum is restored. It should still work ok as long as the diaphragm doesn't rupture.