I replaced the donuts and bushings on the driveshaft hoping it would stop the bucking this car does sometimes, but it didn't. It seems to happen in 2nd through 4th gears when lugging the engine down. It feels like if you stepped on the gas, let off, stepped on, let off, etc. It will get worse with each pulse if I don't either up shift or push in the clutch, to the point of real violence. I've had plenty of different cars and trucks but none that acted like this. Any ideas?