Transmission Question

[jessewebb]

I have a 69 C/10 it has a 350 Small block with a th350 transmission. I change the rearend that was in it. Put a posi 373 in it. My problem is, I'm geared to low now. I would like to go with a 4 speed automatic transmission. one with O/D. Is that a 700R. I read in a thread I'd need to move the crossmember back, and no doubt would have to change the driveline. Anyone running this setup. Or have an idea on what I need. I like the low gear rearend, but still need to run the interstate from time to time. Thanks for any advice in advance

[benoit454]

well if you have a 9 inch tail th350 then it's alot easier. The 700r4 and the 9 inch th350 are almost the exact same length and your driveshaft will work. if not then you need to have your driveshaft cut down to fit. trans cooler lines should be fine, they are in the same spot as the other, the crossmember would have to be moved back some and the right mount for it, not sure if the 350 is the same or not. I'm pretty sure I had heard the linkage is fine, and works, it's just od would be shown as d on your indicator and d would be 2 or whatever.

Pretty sure the rest should be easy, except for the lockup, you'll need a lockup kit, b&m tci and others make them, some make their own.

I know I'm not too much help, I've never done the swap, but I have removed a 700 and put a th350 in it's place in my 4x4.

[67c10rustbuket]

Is that a 700R.

Yes close enough, it is a 700R4 actually.

pretty straight forward but the original trans will determine how far you need to move the crossmember and shorten the driveshaft. I think the trucks originally had a "long tail" TH350 while cars had the "short tail" TH350. im sure someone else has better info dealing with these trucks im using a manual trans in my truck.

I converted my 59 wagon to a 700r4 and the mount was around 4" back from the stock location, but that was long before the TH350 and a car not a truck.

and you must get the lockup kit or it wont work properly.

[benoit454]

it'll work it just won't lock up. Alot of ppl debate it. Some say it'll burn it up fast, some say it won't. Bottom line it locks up the clutch inside the TC and that saves gas, saves slippage, and slippage is heat, heat kills trans and convertors.

As for the different length tails effecting the mount location, no, the mounts bolt to the case, not the tailhousing, at leasty on the th350 they are, pretty sure they are on the case of the 700r4 also.

It is off though an inch or two.

they had 3 length th350's a 12 inch which is kinda rare and from what I hear in vans, the 9 inch which was trucks and some cars maybe and 6 which was in maybe older trucks and then cars for sure. The 6 inch short tail would need the DS shortened around 3 inches, the 9 inch would not need shortened since it's the same length as the 700r4. The 12 inch if you had it would mean you need the DS lengthened to work.

[67c10rustbuket]

oops ! the mount IS on the case as benoit said, NOT the tail housing as I previously said.
sorry ive been staring at my saginaw 3 spd and muncie M20 4spd too much lately, they do have the mount on the tail. and in my 59 car i went from a 3 spd manual and I6 to a 350V8 and 700r4 to clarify.

[jessewebb]

Thanks for the info guys. Very helpful

[karlbenz]

as far as the lock-up, you could just put a toggle switch on it. pretty simple. just don't forget to switch it off when slowing to a stop