Transmission help?
 

So I rebuilt my 1st engine (Olds 455) AND transmission (th400). The engine is running fine, but today is the first time I've shifted it out of park (procrastinated in fear of my transmission rebuild being unsuccessful). I have my '64 on jack stands with no rear wheels in these situations. I am using Slick Shift oil in the tranny.

I have two problems:

1. If I shift into Reverse and leave it in reverse the engine dies.

2. Shifting into Drive works, but once I bring the RPMs up over 2000 the axles immediately stop causing the engine to stall.

What is most likely screwed up?


***Because I feared this I did buy a backup th400 that does work.