Hey RussIt is probably that the throtle cable is miss adjusted or the modulator has oil in the line indicating a bad modulator. GoodluckJoe. GoodluckJoe
There isn't a modulator. Chrysler doesn't use them. Check trans electrical codes, maybe bad reading on output sensor or solenoid. Always check for codes first. Can save a lot of work and $. Dan the tranny man.
I had a very similar problem and it turned out to be the Output Shaft Speed Sensor.