I took the 4L60E from my 1995 z28 and bought a monster-in-a-box rebuild kit and it came with a shift kit. My transmission kit was the one rated for 500 hp. We installed everything and included a 2000 rpm stall converter. Now the transmission won't move in drive or overdrive. It works in first and second. When we put it in drive or overdrive it acts like it is in neutral. We can get the transmission to go into third and fourth once the car is moving by bumping it into drive but once we slow down then it acts like drive and overdrive is neutral again. Any help?

 

forward sprag. broken or installed wrong.

 

Yup... Input sprag is rolled or in backwards or you have an issue with the forward clutches not engaging.

Frank