Why would anyone switch from a 700R4 to a TH350. From my understanding 700's are better.

 

Define "better".

"Better" strength? No.

"Better" gear split? No.

"Better" aftermarket support for racing purposes? No.

"Better" fuel economy? Yes.

"Better" SOTP feel for showroom effects? Yes.

 

I thought they were built
oh well.

 

When the TH700 was first introduced in 1982, it took 3 years of warranty repairs before the factory started getting their act together. Almost all of them from those first few years were rebuilt or trashed. By the 1988 model year, they were able to handle "normal" power and "normal" use. However, I know a guy who has his own corner of a Chevy dealer's shop who does nothing but rebuild transmissions all day (and he doesn't even remove or install the trannys in the vehicle). The vast majority of his work, he says, is TH700/4L60's.

When the TH350 was introduced in 1969, they just worked.

Is it possible to build up a TH700 to handle decent power? Yes. But, you can build a TH350 to handle more power. For a lot less money.

If you want an overdrive transmission that can handle a bunch of power, you're looking at a TH200-4R or 4L80E.

 

My 30,000 mile rebuilt 700R4 lasted about 10 miles of abuse behind my motor. I got a TH350 that sat out in the rain in my friends backyard for years, took it to another friend who cleaned it up and did a $250 rebuild on it with some tweeks. Works flawlessly, hooks better, and no more crazy-RPM drop during shifting. Forget overdrive.