2000 Stratus Tranny

This car has only 80k miles on it.While driving I started to hear a whine that was consistent with the engine speed.Ounce stop the car jump in and out of gear.Fluid level was ok.Dealer who I didn't trust said the converter was bad and complete was rebuild was needed.
I changed the input tranny speed sensor but not the out.could it be the solenoid pak? Also the drives fine if u let it sit but then starts the problem again.:banghead: