Dec Hot Rod has an article on a Buick GS. Its running 11's with factory exhaust manifolds, heads, etc. Anyway, it mentions that he's using a TH350C with a lockup converter. Never heard of that one! Anyone know anything about it? Also, its known that the TH350 consumes less power than the TH400. Anyone have a ballpark figure on the difference in power consumed?

its just a th350 with a lockup converter

so besides the converter, wiring harness and TCC solenoid, its the same thing (and input shaft too i guess)

they came out in 1980 i believe

So, I wonder why they are not more widely used or heard of?

Because there were very, very few produced; and both of the people who have them apparently want to keep them.

There's too many variables that affect the loss in an auto trans to make a blaket statement about it; but a 350 built to the same clutch pack tolerances etc. as a 400 will lose about 2/3 as much power within itself. It would typically show up as about 6-10 RWHP.

So, would it be possible to convert a standard TH350 to the TH350C configuration?

i have a T350c in my garage right now.

Can this thing handle as much power as a non-lock-up trans? I ask because it will be going behind something pretty stout. Just wondering since no one around here can tell me anything about them strength wise. Any problems with not hooking up the lock-up and running a non-lockup stall?

Pro Built Automatics, do you have any insight?

Yes it is possible to "convert" a 350 into a 350C, in 2 easy steps:

1. Remove 350 from vehicle
2. Obtain and install 350C

However it cannot be done using the same transmission.

I don't recall them being very popular back when they were a current product, although it's been so long I don't remember why. I seem to recall issues with lockup clutch reliability but I could be wrong. My memory isn't real clear. They say when you get old, your memory is the second thing you lose; problem is, I can't remember what the first thing was. Anyway, nobody used them for high-perf applications when they were still somewhat plentiful, for whatever reason; but I suppose you could try it.

so what would be the sale value of this transmission then?

Would a th350 consume less power than a 700r4? and be lighter?

th350-c are extremely common, are in about everything 80-up, are small engine versions and larger engine versions, so watch out, i have one from an 81 c-10 pickup that was 5.7L oldmobile diesel equipped, ran very good, is a DX model heavy duty th350-C, i am aboput to put it in my 81 c-10 thats originally 250ci and SM326 on the tree shift manual, i have a driveshaft 3" shorter so it will work cuz the 326 is length of short tail th350(IE cars only)


you ppl with these cars swapping to th350 from 700r4 are not smart by using car th350s when ytou could be using truck ones and then not need to change your driveshaft

but i guess car ppl dont know as much about what GM did across the lines

oh and most of the th350-C are dual pattern bellhousings- 10 bolts, will bolt to diesels, oldsmobiles, buicks, caddies, pontiacs, chevies, etc,

so if i ever come across a gas olds 350 or 455 or 403, etc i will put it in the 81 c-10 too for the lower rpm torque i need to haul with, i hjave the stock 350 diesl mounts setup and p/s and alt setup from the diesel that will bolt right to an oldsmobile v8

gm made everything stock form so yuo can put any division of gm trans or engine into any make model of gm vehicle

ou just have to stop and think about it,

it all exists and was done and made, at some point or another

the diesel 350 was 78-85 years, caprices, caddies, olds, c-10 pickups,

and some others,
very common



good luck

double oops

My only complaint about the TH350-C is that there are not many aftermarket kits out there. I'm going with a B&M stage 2 kit, but would have preferred a manual valve body. Other than that, the trans is great, lockup works great, and MPG still much worse than a OD trans.

No. The case, VB, converter, and input are all different.

In regards to being able to hold up under power I have one in an 04 GTO putting down 650 rwhp lockup works very well. I use a Vig 3900 multi disk converter. The trans is full manual and when the converter locks WOT it drops ~400 rpm and it feels like it shifted into another gear. With the roll bar and frame connectors this car weighs in at 3850.

if you want to use the 350c with no lockup leave the connector disconnected and it will work like a th350. Power upgrades can be made to the 350c like the 350. If you want to use a th350 stall converter cut off the tip of the shaft of the 350c. some 350c's came with a lighter sun gear drive shell with lightening holes. For high horsepower over approx 375hp a better sprag drum with hardened race, and bolt in center support should be done along with minimum 5 clutch l/r, forwards and direct clutch packs, 3 clutch intermediate. The 350c had bearings to replace thrust and saves even more power. Shift kits not many but enough to be good. Most just drill the separator plate and replace some v.b. springs. The 350c happened in the smog era. but got complaints for harsh lockup in grandma cars, so shops would disconnect the connector and claim alls good and the customer would be none the wiser.