My 95-3.1 started this odd shudder and rapid surging ( nearly twice per second ) when the converter tried to lock up. I could hear a noise during this surging. I don't know if I would call it a thumping. The tranny shop replaced the converter because it couldn't hold during lockup. It showed signs of excessive slipping and heat. It works great now except it seems like it locks up kinda hard and fast, with a jerk. Does anyone know if the lockup is supposed to be with a jerk or velvet smooth. When I first got the car it locked up so smoothly I couldn't feel it at all-- had to watch the tach to be sure it was locked. Maybe that's why it went out...it was already starting to begin slipping.