I have a 2000 Chevy Venture, lately when the weather gets warm out and the car has warmed up, the transmisson will start to whine and shift very hard. The engine tempeture will also rise to as well, often into the red. HELP!
I would first concentrate on the engine. Since the transmission cooler is inside the radiator, the transmission will overheat if the engine overheats. Check your cooling system, radiator cooling fans, thermostat, and check for leaks in the radiator, hoses etc. Dont let that transmission run hot, anything over 200 degrees will slowly start to damage it.
Also, scan the computer for codes. The hard shifting and whining is most likely due to the transmission being excessively hot and the computer is trying to keep it from burning up. A scan will tell me for sure. Take it to a local auto parts store, most of them will scan the computer for free. Post back with the code/s and we can go from there.
transman