My thoughts on the subject would be a potential loss of pinion bearing pre load related to the stock crush sleeve which has now changed your backlash allowing the clunk. Hard launches or manual shifting with increased power on our cars can certainly do that. Hence my second rebuild on the second...
I have 4.56s in mine. I couldnt drive the car with the stock tune and the shifting felt all off because torque management was fighting it something awful. I could make it to about 45 at 1/4 throttle before it just fell on its face.
My tuner was able to make it happen locally. Both lund and...