I was having the problem so I changed the autotransmission and the car still wouldnt go uphill in drive gear with car get hot. Only in reverse why?
I’m not sure if you are saying the transmission is slipping when in drive, or that the engine isn’t making enough power. One way of checking this is by checking for severe exhaust restriction. That will allow the engine to start and run ok, but not be able to make sufficient power.
I’d recommend getting the vehicle inspected by a professional mechanic. They will be able to properly diagnose your loss of power and make the necessary repairs to get your car running normally again.