The car will vibrate in a pattern rumble, rumble, rumble, "pause" rumble, rumble, rumble, "pause" and so on. It starts at about 55mpg. We ran it up to 70 and it does not get much worse. I let it coast at that speed, Kicked it in neutral and as long as it stayed over 55 it rumbled. We had the tires balanced. it might be coming from the front left, not sure Thanks, Jay