va454ss

iTrader: (1)

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?

1991tealRSt-topGuy

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

va454ss

iTrader: (1)

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

RB83L69

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.

va454ss

iTrader: (1)

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

xpndbl3

iTrader: (5)

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?

va454ss

iTrader: (1)

Pro Built Automatics, do you have any insight?

RB83L69

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.

xpndbl3

iTrader: (5)

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

88Camaro350

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

Randy82WS7

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

Randy82WS7

double oops

CrazyHawaiian

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.

jmd

iTrader: (4)

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

DadsYellowGoat

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.

ed o

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.

Kiwi Cutlass

[QUOTE=ed o;3979761]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.
Hi there, you have made my year! To explain euphoria - after much study I placed an order for a TCI high stall torque converter
with Summit Racing. 2 days before it arrived on New Zealand I discovered the trans in my '65 Cutlass is a TH350C so the new torque converter will not fit. I came to the conclusion that the best way forward is to change out some parts eg input shaft,pump etc to create a TH350.After seeing an image of the TH350 and TH350Cs input shaft I wondered whether I could just cut off the lockup spline section on the shaft to allow me to fit the TCI TC and after much more searching found your comment re this idea.Feeling optimistic about now and am thinking about cutting the shaft with my angle grinder fitted with a good cutting wheel.Can you please confirm that this idea will work and advise of there are any other changes required? Thanks so much in advance

87zjeff

iTrader: (4)

[QUOTE=Kiwi Cutlass;6096896]i wouldn't just simply cut the pilot off the input to allow the use of a non lock-up converter on a lock-up unit. pump itself is shorter and will not engage the splines in the converter completely.

Pro Built Automatics

The TH350C (1980 - 1986) can be made to work very well. The 9.5" lock up torque converter can be used here. The internals are the same and came with some better thrust washers (plastic), stator support sealing rings (Teflon), wider front stator bushing, etc. If using a small block with a large camshaft and low rear end gears, the Vega sunshell with the holes on the side, and the input drum with it being machined down on the front third of the drum. This combined with the sunshell will lose you apx. 3 - 3.5 pounds in rotating mass. This can improve the sixty foot times. You can add the late 1987 and later low/reverse support with the .150" wider roller clutch. Machine the direct piston to hold 5 clutches if yours does not already have this. The waved steel in the forward clutch pack should always have 3 teeth and always install this. Do not use the waved steel without these teeth. To improve the 1-2 manual shift, take a used low/reverse clutch and remove the clutch lining, file it flat and smooth and make a cut in it to open it up and install this under the intermediate clutch apply piston in the front pump. If you do not do this you will have a delay on the 1-2 WOT shift, not a slip, just a delay. DO NOT block accumulators here, or remove the accumulator springs. When using the TransGo Performance Shift kit it will reduce accumulator feed which is ok in most cases. Always install the waved intermediate steel, as this will prevent the sprag race from breaking. On the accumulators the cast iron sealing rings work well. Stator support sealing rings to use here are the Teflon and they do not "knife edge" as the cast metal rings do. Always use the plastic insert on the output shaft to input shaft for lubrication. Install the wide direct drum bushing and the bronze case bushing. You can use the Teflon extension housing bushing here, just polish the driveshaft yoke to a very fine finish. Add the triple lip Vamac seal to the extension housing. Use plastic thrust washers where possible instead of the metal thrust washers. If you have access to the Buick TH350's you will find the front planet that uses a bearing instead of a thrust washer. There is an output ring gear hub that uses a bearing also. Clutch clearance for forward .020" - .045". Direct .060" - .080". Intermediate .030" - .040". Low reverse .040" - .060". In low/reverse use the 4L60E low/reverse Turbulator steels for less drag. Use the band with the extra weld. Install the TH350C filter as this filters out much smaller particles. Add two to three magnets to the bottom of the pan. For clutches Borg Warner's do very well here. Use Dexron type fluid here, synthetics are fine, not Type "F". All these improvements make for much less metal in terms of wear when compared to the early TH350's, and much longer transmission life.

Kiwi Cutlass

Hi there, it would be great if you could comment about my post regarding cutting off the tip of the 350C input shaft to enable fitting of a standard TH350 torque converter. Please check out "ed o's and 87zjejeff's posts re this above your on the page.Would like to know if this is possible or not.Thanks in advance for your help.

Pro Built Automatics

I never modified the 350C input shaft and its been so long since I have seen one that I cannot comment here on that modification as to what needs to be done. From what I can recall, you did not do anything to the input shaft, but I could be wrong.

Kiwi Cutlass

[QUOTE=87zjeff;6097201]Well it's been awhile but I'm back looking at modding a TH350C to take a TH350 torque converter. Your comment about the pump being "shorter" which I take to mean thinner when looking at the transmission side on is the first time I have found a reference to this difference.What do you base your statement on?