My GC used to slip gear when the engine would warm up. I brought it to the dealer for a fluid and filter change. It took them 4 hours and cost me $275 and it didn't help the problem. I brought it to local mechanic and he discovered that 2 of the bolts on the transmission housing had worked loose and that the transmission was actually starting to pull away from the engine. He tightened them up and it's been fine ever since. It's worth checking. My experience is that most of the GC problems are silly problems like loose wire harnesses and bolts rather than expensive sensors and computers.
when transmission is cold it shifts to overdrive and downshifts normally.
But after driving for 20 - 30 minutes it takes longer to shift to overdrive, then when in overdrive it downshifts to third GEAR right after foot off the gas pedal.
i have replaced the speed sensor. and replaced tran filter & oil
so I am suspecting a faulty overdrive solenoid ...
or a faulty Throttle Body Sensor...
what else should i look for?