Ok, I am looking at a 93 Z28, and it has the 700R4(pretty sure thats the name) auto transmission. why did they switch to the th400? Thanks.

 

Your 93 has a 4L60, which is the same as the 700R4. In 94, they added electronic control by the PCM, and called it the 4L60E. Those are the only automatics used in the 4th Gen. Anyone with a TH400 has made a conversion, using a casing from one of the 70's and 80's GM cars and trucks that the TH400 was used in. The TH400 is a 3-speed auto, with no O/D.

 

They didn't switch to the TH400. The 1993 uses the 4L60 (basically a 700R4) and later years use the 4L60E (electronically controlled version of the 4L60). I always thought the 700R4 was an overdrive version of the TH350.

The TH400 is a beefier non overdrive 3 speed auto that was used for years in GM higher torque appications. Nowadays it is comparable to the 4L80E that is used mostly in trucks.