Did they set the tourque preload on the diff? The plate diffs require an additive for the oil and I there is a brand of oil every one goes on about that I can't remember off my head. Reduces the noise. Once you put your foot down round a bend you don't care about the clucking! They are awesome for putting the power. They don't clunk all the time. Only at low speed, say pulling out of a parking space and going round a corner real slow. It's funny because people look at the car and think some things wrong. Like the noise the Orc and blitz clutches make