I still have not figured out my TH400 problem. I need to overfill the trans by 2 quarts to get it to shift right. If Im at the proper level it will shift soft and slow or not go into gear at all. I put in a new high flow brass filter figuring that was the problem- still no change. The only thing I can think of is that the pump is going bad.
When shifting all my other automatics (th350, & 4l60e) from park into drive or 1st, the car will lurch ahead. When my put my TH400 into 1st, it doesnt move at all- you wouldnt even know its in gear until you give it some gas. Idle is set at like 700 too. Could that be a sign of low pressure in trans?
Trans is built with reverse valve body and shift kit. Works fine when overfilled, but keeps blowing out rear seals.