1997 Pontiac Grand Prix transmission problems

Vehicle was pulled over in park with the A/C on. Consumer went to speak with another driver that was pulled over in front of her. Driver was standing in front of her vehicle when the vehicle started rolling forward, it slipped out of gear. Consumer was injured in the incident, her leg was pinned between two cars. The dealer cannot duplicate the problem. They stated defect in design.

97 grand prix, 3.8l high output engine,4t65e 4 speed automatic transmission, se model 4 door. Transmission was at first hesitant to go into reverse at 100,000 miles. Around 125,000 miles the transmission has no reverse or neutral movement while pushing the car in reverse. In other words you cannot move the car in reverse at all, even with the engine off and in neutral. Shop told me I had a broken reverse shift fork.