Hi.

I have a '94 Z28 A4 and few days ago the car started making a terrible knocking noise...
The noise comes from the rear and I think it's coming from the passanger side, but it's hard to tell.
At first it only made this noise when giving gas but now it also makes this noise when slowing down (around 20mph and down).
The more gas I give it and the faster the car goes the faster the noise is.
It does not make this noise when the car is stop and reving, only when it's in drive.
I don't think this noise can be heard from the outside, at least I can't hear it if I open the windows and stick my head out, but from the inside it's terrible.

Do you guys have any Idea what it could be. Fuel pump? Gears? transmission?

I recorded the noise. The quality of the file is poor but still helps.

Click here to hear the noise

Thanks in advance!

 

Check your rear tires; make sure you did not pick up a nail or rock inside the tire threads, however that nose could be your rear end differential.

 

Not knowing what speeds you were going during any time of the recordings and judging by the frequency of the sound, I would say it might be a u-joint. I wouldn't drive it until I found out what it was. Maybe put the rear up on jackstands and try to isolate the sound.

 

when u give it gas is the front of the rear end loose and torqueing upward into the floorboard...jake it up and look...listen...

 

I second shoebox Don't drive it anymore. I'd check the U-joints and the wheels to make sure they are properly seated

 

sounds like a bearing noise posibly rear axle or pinion bearing