Just wondering if anyone can help me diagnose my problem. After I get up to highway speeds (70-80mph) I get what I think is like a hard vibration that is coming from the middle of the car. Like right underneath the divider between the floor in the backseat. When I accelerate or deaccelrate with my foot on the gas it doesn't do it but if you take your foot totally of the pedal it vibrates real hard or something. Once you get under 40mph after that it doesn't sound as bad or happen as offen. Also happens at slow speeds when I'm in reverse. Anyone ever heard of this? I've had it jacked up and have been underneath it and don't see anything out of the ordinary.

Thanks

 

sounds like either you have a bad rear wheel bearing, or a bad rear tire.

 

I thought it might be the wheel bearings too but though it might be something else since I cannot rock the rear tires at all and the sound goes away as soon as you touch the gas.

 

leam more twars checking wheel balance, if you have a bad tire or maybe even one of your wheels may be warped.