!994 300 six e4od revs up and down while in overdrive about 50% of the time. The transmission was rebuilt with a new torque converter installed. I have talked to the transmission guy (who by the way is well respected) and he seems to think that it is a sensor that is causing the problem for me to bring it back (for another charge, I'm sure). My question is what bad sensor could cause this?

 

The Transmission Range Sensor (TRS) could cause this. It used to be called the Manual Lever Position Sensor (MLPS.)