I have a 2000 Z28 with a A4 transmission...I noticed that it knocks in my rear end, but...it only does it when I'm not on the gas or on the brakes. When I'm coasting it knocks pretty loud and it comes from the rear end and if I pull out abuptly it has a loud knock.

 

Exactly what mine did, it got louder and louder until I replaced it.

 

What did you replace?? The rear end...driveshaft...gears

 

I had a similar issue once. My cross shaft retaining bolt had came out and was wedged b/t the carrier and the ring gear. The "thuding" mine was making was coming from the pinion gear hitting the bolt on every rotation. Im very lucky the cross shaft didnt come out.

I would jack the car up and check. It is going to be either a u-joint or something in the rearend. It could just be a bearing. If the U-joint feels good, run the car in gear up on a jackstand while safetly taking a stethoscope to the rearend near the bearings. This will help you pinpoint where the noise is coming from. And please use a friend to help.

 

Well my back driver's tire was loose to the point it snapped two studs, good thing it didn't fly off. I have no clue how I didn't see this...what a idiot I am.

Anyway, still had a pretty loud bang whenever I accelerate really hard..but no knocking while driving

 

For the bang, check your torque arm bolts and front mount. The mount is probably most likely. It can be tough to tell visually, so also look for witness marks where the arm is hitting the floorpan.