This has me stumped. My 1970 SS 396 L34 Camaro with TH400 transmission vibrates (it sounds like it is the back passenger side.) when I am stopped at a light. When I drive it their is no vibration. I thought maybe it was the TH 400 mounts, but if that was it, then the car would vibrate when I am driving which is not the case. It seems strange to have vibration when the car is at a standstill. The TH 400 is not turning, the drive shaft and rear axle also are not spinning. It makes no sense to me. Maybe a member might have an idea. When I put the Trans in neutral the vibration stops. Thanks John.