Recently i posted an issue with a vacuum leak. The solution worked. Now im focusing on a bad pressure control solenoid, or so i hope. My car every now and then will shift hard, as if the pressure in the transmission fluid is drawn off. I have also heard this is or has been a catalyst to having your tranny rebuilt. Also, i have heard that this problem could be a shift clutch or something. My question is, what type of transmission is in the 2000 Pontiac Grand Prix SE with the 3.1l in it. Im pretty sure its a 4t65. I want to try the solenoid first, if not, ill sell the car. Thanks for all your responses.

Yes 4t65e. This thread has some more info on different year tranny's.