95 Sonoma 4x4 no reverse after rebuild.

I rebuilt this transmission for the second time and when I put it back together and into the truck it will only move in reverse on a flat surface and it feels like its trying to engage but doesn't.Also I have a slow 2nd to 3rd shift,very slow and sometimes it sounds like its in neutral if I rev the motor.Only got 40,000 mile miles out of the last rebuild.Any ideas?I'm dreading taking that thing back out and apart again.

I feel your pain. Just got through rebuilding mine. Still has original problem. On mine it appears the input sprag is slipping. Oh well, it's back up on the jacks and back on the floor for me. Even after passing all of the preliminary air pressure checks on the clutches you can miss some things. Good luck.