I have an '89 5.0 HO 5 speed and under acceleration it vibrates or shakes like it has a flat rear tire. It is most noticeable in second gear but is always there when accelerating. It is a low mileage (53,000 miles) California car and I can't see anything wrong with the rear suspension. It has new tires and new wheels (Ford replacements). I'm thinking maybe the driveshaft . ? Is there any kind of history of driveshaft problems with these models ? Thanks in advance for any help or advice.