Turbo 350 C trans

[Boog]

I have this trans but no idea what it came out of. It is currently in my 69 C10. Was this series a short run or is it identified by different number maybe? Good/bad trans?
I don't see it listed anywhere like Summit or Bowtie Overdrives.
If I do decide to use it it needs a rebuild and complete lockup converter wiring kit. Anybody?

[Bigdav160]

The addition of the lockup converter made the TH350 less reliable. I always add a shift kit that disables the lockup function. It is not needed like in an OD transmission

[Tom]

I've never heard of lockup problems in the Th350c, but then again they aren't super common.

[clinebarger]

Nobody uses them, They are just different enough from a standard TH350 to be annoying.

There are different ways to wire them, You can use a Governor Pressure Switch (Most stock ones use this), Or Use a pressure switch on the 3rd gear pressure tap on the outside of the case, If you decide to rebuild it, I will help with the wiring if needed.

But I recommend rebuilding a regular TH350.

[Boog]

Yeah it's an oddball alright. A buddy who rebuilds auto trannys said according to his book there is nothing that will interchange between this C and a plain 350. I don't know that I have ever seen one before and I'm 61.
Anyway I found a little info on it and see it was manufactured between 69 and 86 and installed in Chevelles, Caprices and trucks.
Is that wiring plug on the side the same as the ones on the 700R and 2004R? Are they all four wire? So will the lockup converter kit for the 700R work on this C?

[TransMan1972]

Check the FAQ posts on this forum, I believe someone already done the work for you...
GM was field testing the Torque convertor clutch within the TH350C to assist in designing the TCC for the later release of the 700R4 is all....they found how the clutch reacted to early engagements at lower road speeds and how it impacted TC clutch and trans life cycles....

Just to add to this info....GM did not use the term "LOCKUP" back in the day...it was used by Chrysler.... GM referred to the Torque Converter Clutch, not LOCKUP....Thanks for listening!!!!

[clinebarger]

Originally Posted by Boog

Yeah it's an oddball alright. A buddy who rebuilds auto trannys said according to his book there is nothing that will interchange between this C and a plain 350. I don't know that I have ever seen one before and I'm 61.
Anyway I found a little info on it and see it was manufactured between 69 and 86 and installed in Chevelles, Caprices and trucks.
Is that wiring plug on the side the same as the ones on the 700R and 2004R? Are they all four wire? So will the lockup converter kit for the 700R work on this C?

The TH350C didn't show up 'til the late 70's.

The Case, Pump, Input shaft, And has a Auxiliary Valve body that houses the Lock-Up valve & TCC Solenoid, All the drums, Planets, Center support etc. will swap out.

If one shows up at my shop....I just rob the Direct Drum & Forward Drum out of it & Scrap the rest.

I don't pay much attention to them, But I believe they have a 2-pin Case pass throughs, A 700R4 lock-up kit won't do you any good, You can get it functioning without a kit.

[Boog]

CB I don't know if I mentioned it here but this trans was bought used and put in a mid 60s truck. That was 30 + years ago. It had problems right away so we yanked it right back out and put another one in. This one was pushed in a corner and thought it might be used for a core some day.As I remember this trans slipped shifting. The fluid is still pretty red and doesn't smell burned. Fast forward to a few years ago. I had the engine built for my 69 and needed a tranny so I put this one in just to set everything up. I had bought a T350 to rebuild for the truck but that one was total junk, even bad case. So now I am giving thought to getting this C trans to work since I already have it. Worth a shot, right? It's not ready to roll out of the shop yet to test it. Working on brakes.
This truck will never run down the strip and won't be a daily driver so might this trans be worthwhile for light duty? The truck is listed in my sig line.

[clinebarger]

It will be fine for your truck, They can be built to handle as much power as a standard TH350, Just limited on torque converter selection, But that is not a concern for you.

[Hart_Rod]

Bringing up an old thread. Looks like I have one of these in my 84. The lockup is engaging to quickly unless I keep my foot in it. Is there a way to adjust when it locks up? TIA

[Ziegelsteinfaust]

Originally Posted by clinebarger

It will be fine for your truck, They can be built to handle as much power as a standard TH350, Just limited on torque converter selection, But that is not a concern for you.

A torque converter shop can custom build one for you many times.

Factory there is essentially 2 converters I believe. One for cars, and the other for trucks.

My friend had a 80? C10 with one, and we were able to get close to 2500 stall for him. Worked pretty nice with the factory gears, and 4/6 drop.

Swapping a car version is like 1800 vs 1600 of a truck.

I used a car version in a C10 I had when I found out what it was, and decided to try it. The truck was built to mpg on the open road as I constantly going on fishing trips at that point in my life. I was doing 4-5 hour trips one way twice a month in spring to fall, and about once a month in winter.

I did like them, but today a th700r4 is a better choice. With my preference being the 4L60 being built to 65 standards atleast.

[pjmoreland]

B&M makes a speed-based TCC controller that you could use on your TH350C.

https://www.holley.com/products/driv...er/parts/70244

I designed a speed and vacuum based controller for my 700R4 that is similar to the B&M unit but it also unlocks the TCC during acceleration. Member HO455 is in the process of trying one on his TH350C.

https://67-72chevytrucks.com/vboard/...=822382&page=5

[AussieinNC]

TH350-C has a convertor lockup valve and most have a lockup pressure switch that raises TCC lockup timing.

Higher pressure switches equals higher lockup speeds.

Standard is 38psi, highest available is 58psi.

Check the wiring to the switch is intact and not broken.

The description you give of higher speed lockup only if you are into it tells me the switch may be faulty or has a wiring issue.

Hope this helps
see page 1 of Transgo kit installation

https://res.cloudinary.com/transgo/wbiss/sk/SK350.pdf