I have a 89 700-r4 I just rebuilt the problem is now it slipping in both first and reverse at low rpm. also shifts late or only when I let off the gas What did I do wrong ??

 

The first thing to check would be to make sure the kickdown cable is connected at the tranny and adjusted. That could cause the bad shifting. As for the slipping, the easiest thing to check after that is to remove the valve body and double check everything there - make sure all the ***** are in place and the gaskets're good. After that there are some seals either on the input shaft or the pump (somewhere at the front anyway) that are easy to mess up. I messed those up once and it cause some slippage in reverse. Good luck.