Got another question this one has me stumped. I have a 95 impala with 150 thousand miles . Win you are driving down the road at a constant speed it shakes real bad. You can feel it in the seats but not in steering wheel. If you give it gas it stops , same win you let off the gas. I have already rotated the tires and pulled the drive shaft to check u-joints. Everything looks fine. Thanks for any ideas.