Rhodetd

I have a 1970 cutlass supreme conv. Right now it has the original 350/th350 and Otype rear with 2.56? gears. I have a 70 455 I plan to install. The tranny needs a rebuild. The question is should I rebuild the th350 or put in the th400 that came with the engine (after rebuild), or spend alittle extra on a 200 4r? I also have a corporate rear out of a 72. I know that with either the th400 or the 72 rear I'll need a new driftshaft. I don't mind spending alittle more to get it right the first time. Given those options what combo do you guys suggest?

oldcutlass

Choices, choices, I've heard of a lot of happy campers with 200R4 swap and some new gears. It's the best of all worlds in the long run, but costly.

svnt442

It the original rear a posi per chance? I had a 70 with a 2.56 posi and I did the 455/400 thing with that car and never swapped the gears out. Lets just say I had a lot of fun with that car and it was a good thing I had access to take off tires.
What you could do is drop the 455 in front of the TH350 for a while until you get your trans situation sorted, unless you think you can wait.

oldstata

What gears are you going to run it will help I believe the 200r4 has a over drive gear so you could go steeper on the gears like 3.90 and still rev low on the high way

Rhodetd

I see a lot of posts about putting a 2004r in other cars, but not a lot in 68-72's. Other than the TV cable and maybe shifter(floor), are there any issues I should worry about? By the time I rebuild the other trans the 200 is $500-$700 more?

Rhodetd

It's an open rear. The th350 is on its way out, won't go into gear cold and makes a squealing sound when shifting.

oldsman72

You need to change your driveshaft if you swap from a TH350 to TH400 (and vice-versa)?? I thought they were the same size?

joe_padavano

Nope. The TH400 is longer. The 200-4R uses the same driveshaft length as the short tail TH350 but the crossmember uses the TH400 location.