I have no reverse. Runs and drives forward , when i apply brake and shift gears : from Park to Reverse you can feel it wanting to go in reverse plus the rpm guage changes slightly: from Reverse to Nuetral same thing : Nuetral to Drive makes one hell of a bang and engages with wheel spinning in reverse no wheel spins.

 

other than fluid level and linkage adjustment out of position I would say trans is going south. that said I did not get into auto trans in school so I know very little about them.

 

Sounds like a broken reverse band based on your description. It could be other things. Honestly none of that matters. There are no adjustments or things you can fix for reverse externally. Since it will be an internal issue any transmission not under warranty should get a full rebuild. Once you open a transmission cleanliness is critical. Very few people would spend time cleaning everything in the transmission to put it back together with used parts.