Originally Posted by Keninyuma
I live in Yuma, AZ with VERY hot summers which somehow effects something that causes the car to seem like the transmission is slipping. Strange thing is that it only happens now and then when it is very hot outside. The rpms will rev up and the car will barely move forward but it's ok in reverse. I have replaced the throttle position sensor several times which seems to help for awhile but I never know for sure because its so erratic. Engine is 4.0 in Grand Cherokee. Has anyone had this problem or know how I can track it down? Please help.
Year, mileage, any known prior transmission service would be good to know.
Have you checked your transmission fluid fill and condition?
If this isn't your vehicle from new, is it even the correct type of ATF for that transmission?
When it slips like that, can you stand the heat long enough to pull the stick and see if there is any foaming? That can cause the transmission to pretty much refuse to move the vehicle. That reverse works sounds more like something inside the transmission getting a tad old though...