Tranny swap?

[JimIsbell]

Is it possible...easily...to replace the TH400 with a TH700?

OK, I found the answer.....maybe. Its easy, but is it desirable?

But I see that the 200 is also a possibility and maybe easier?

The car I am considering doing the swap on is a 70 454 so is the engine too big for a 200?

 

[TLTONEY]

Did you ever get an answer?

 

[damoroso]

I find the 200 easier, but that's me. It's physically smaller so it fits in the tunnel better, and IMHO the gear ratios are a bit better for a daily driver, If your engine is stock or less than about 350hp, or so, you should be fine.

 

[TLTONEY]

Did you use a stock 200 or was it modified for the BB?

 

[Hib Halverson]

It is relatively easy to replace a TH400 with a TH700R4 (aka 4L60) because both were offered at different times in a C3.

Only problem is that the TH700 would not be reliable behind a big block unless 1) it were substantially modified and 2) the big-block was either stock or mildly modified.

The problem is that the TH700's input torque rating is not near high enough for a BBC.

As for the TH200...that might be more work to install and may have some of the same problems with reliability/durability when used with a BBC.

 

[damoroso]

I modified my 200 a bit, but that's because the BB is modified as well. These transmissions were used in Buick Grand Nationals, and have done well, so they can handle performance applications. Again, either will work and work well provided they're built appropriately. You don't want a bone stock 700 or 200 behind a 500+ HP engine, big or small block.

 

[TimAT]

I modified my 200 a bit, but that's because the BB is modified as well. These transmissions were used in Buick Grand Nationals, and have done well, so they can handle performance applications. Again, either will work and work well provided they're built appropriately. You don't want a bone stock 700 or 200 behind a 500+ HP engine, big or small block.

erd:
The key is to build the trans to handle your expected hp/tq. I've seen both 200-R4's and 700-4R's handle some fairly big numbers. If they break, they break. I've seen TH-400's look like a grenade went off inside them too.
An advantage (?) to a Corvette is that "most" of the time, with one that's making some good HP, is that if the rear tires really hookup, the rear end gets picked up with some oil dry and a shovel.