OK, ive got a 99 LS, and when i drive it theres a sort of thud-thud thud rumble coming from the rear, the faster you go, the faster the thud goes, until its just a rumble. Ive coasted down a hill with the using the clutch, and i could still here the rumble, so were almost positive its coming from the rear tire i think it might be a problem with the tire, but im not sure and was wondering if you guys would have any insight or advice as too what the problem might be.