th350 question.
 

I have seen info stating that Pontiac put the TH350-C in some 81 birds. Maybe in the V-6 cars? Anyone verify one and what is engine its connected to. Thanks!

cant say on the v6 cars for sure, but all 81 birds had the th350c as far as i know, it was part of the computer controll that came out in 81. th350c had the lock up converter. my 1981 turbo t/a has the th350c & other non turbo 81's ive owned have had it too.

Yes my 81 T301 had a lock up TH350. Previous owner had taken out the computer so not sure how they drive. I had Continental make a 13" for me that loosened it up a little, but never wired a lockup.
My brother in law back in the early 80s had a 81 Z28 that had one he was always cussing it was so sloppy locking and unlocking.

they shift & drive very good if the computer & internal lock up solenoid are in working condition. shifts just like a normal th350. the lock up is a very basic speed sensor.

i had the stock lock up converter opened up & a little more stall speed added on my 81 turbo.

Thanks for the replies! I noticed on a pick up truck that the vacuum seemed to be involved in the lock up. Wondering if this was the case on the 81 birds.

not sure on trucks, they usually have some differences or a delay in technology vs cars.

on 81 birds it is mph based from a sensor in the speedo that activates an electric solenoid inside the trans that engages & releases the lock up. theres a section on testing & trouble shooting in the GM manual. are you working on an 81?

I bought an '80 a few years ago, had a th350-C with it. I am trying to see how much the "C" helped the fuel economy. I assume the tall gears were the same "C" or no "c"

i havent really tested the fuel economy on mine, when i feel it engage the lock up the rpm drop is barely noticeable, probably because its a tight converter anyways. but GM felt it was worthwhile so id guess there was some improvement in mpg.

pretty sure trans gearing was the same c or no c. rear ratios could differ based on the car, all turbo t/a's got a 3.08 posi, other models & engines were 3.42-2.xx ratios. if thats what you meant by tall gears.

My brother in law had his Z28 at the dealer several times to no help it may have been more and issue of lick unlock while hunting for gears.

I bought a 81 turbo parts car, got the TH350 lockup trans, but no engine (thankfully).
I had a TH350C in my old 67 Bel Air, my first car. Bolted right I place of the original glide. This all sounds silly. I had the 283 properly built by a local engine builder. It got all good parts.
I wanted to put a 700R4 trans in it. He talked me out of it. This was likely the early 90's...
He had been pulling TH350C's out of oil field pickups and install I got TH 400's.

He built me a nice lockup TH350. I had to install the brake switch used on cruise controls, so the converter would unlock with brake applied. There was a vacuum switch that I installed in line with the brakes switch, I unlocked the converter at full throttle.
My TH350C allowed me to cruise at 350 RPM's less....I liked it! Of course my engine builder did a great job on the trans! Wish he had not moved and changed his business focus.

I no longer have the old Chevy, but still have the engine and trans. Still have the Pontiac trans too....

Very cool story! Thanks for the RPM info too !