My 1992 Pontiac Sunbird SE Convertible 2.0 4cyl. 196,000 mls doesn't shift any more after appr. 15 minutes of driving. When the engine cq transmission is cold it shifts smoothly. After a few miles , when I slow down or come to a complete stop, the transmission doesn't seem to shift back. When I try to accelerate again, the kick down comes in with a big bang. If I stop the car, the engine stalls. When I start the car again, I can't put the stick in D, cause the clutch doesn't work? I have to wait for like an hour before I can drive away again. Can anybody help me with this problem? I already changed transmission oil and AT oil filter. That didn't help.