2 times today while coasting around a curve then gassing back up the rpm jumped without car moving, felt like it was in N. i let rpm down and eased into trottle. trans was rebiult 2 or 3k ago. how to test tran computer?

 

That's happened on my RT a few times in the years I've owned it. I think as you are coasting down, the TCU is preparing to shift into a lower gear, then you give it gas, confusing the TCU, catching the tranny between gears. Normally, when a tranny starts slipping...it slips all the time.