It vibrates on the floor when i get to 65-70mph and it vibrates the whole car in a rotating sound. Its not constant loud vibration in one sequence, it gets real bad every second and quiets up a little bit then it gets bad and so forth. I will put it neutral and it gets worse. Then if i put it in fifth it quiets it up a little. I replaced the harmonic balancer and trans mount. Is that the u-joints? Or could my drive shaft be bad? Trans even? Ive only had the car for 2 weeks so i don't know the details of its history unfortunately. Any help would be greatly appreciated! Thanks, Blaine