It's been a long time since I have came here but I'm having a problem with the mustang. I was traveling to see a friend about 300 miles away. On the way I started to feel a little vibration and by the time I got there it was a serious vibration. The whole car shakes at speeds of over like 20mph. The weird part is that if I stay a constant speed around 50 or so, it will get really loud and then completely stop and it will be the smoothest ride ever until I slow down again. The two things I came up with was either the driveshaft got out of balance or maybe the harmonic balancer or something like that. Any info would be greatly appreciated!!
