does this thud happen when you let off the gas without the brake or when you first apply the brakes.
when exactly does the thud happen, info i am looking for is.
1. is there any thunk when you accelerate
2. when you slow down what MPH does the noise happen at? is it when the car comes to a halt, when brakes are first hit or what.
before we condem the rear end itself atleast give us a decent description of the noise. so far I see no reason to suspect the ring and pinion setup.