Had the transmission out during the engine build and had the pump replaced. When I put the car in neutral I can push it forward but not backwards. I can hear something binding (for lack of a better description) in the tranny, as if it's in gear. Put the rear in the air to confirm and wheels will spin forward but not backwards. Any ideas?

 

Some additional info:

Disconnected the driveshaft - rear end is okay.

I had unbolted the shift linkage bracket from the pan, never took it off the bracket itself, then bolted it back in place, and back onto selector. Seems to be shifting okay, but maybe it's off. When it's in park the DS won't turn at all. When in R, N, D, 3, 2, 1, I can turn the DS clockwise but never backwards.