Thumping in rear end.

I just picked up my 97 328i and there is a load and rapid thumping sound coming from the rear on hard acelleration. I was told that this is because the wheels are unbalanced (what kinda fool puts wheels on a car without balancing them). Anyhow, i want to make sure that sounds right before I pay the guy the rest of the cash tomorrow. Any ideas?
Thanks!
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Chevell

well he's right but it could go deeper like out of round wheels,bent rims, to bad tires but like u said he sould have found these problems, another thought if u can and trust me i ain't never seen it but if u can look at the rear half shafts and see if the plastic is busted really i ain't seen much probs from bmw's rear-ends or half shafts but that doesn't mean much.

Rear shock mounts. They usually go bad on E36's, its a common problem. If you hear the thumping over bumps its most likely the rear shock mounts. Just replace the mounts and the noise should go away.

if this is a low rumble when you put the torque to it there may be some actual differential probs or maybe wheel berrings. take it to a reliable mechanic and let him test-drive it, duplicating the conditions.