Has anyone had a problem with 2000 intruders vibrating at speed. It starts at about 45 to 50 mph and continues up to a speed I can't mention. This is BAD, not a little rattle. The mirror in the rear bedroom looks like is is going to fall off the wall. It had broken door supports. Dealer has had tires and wheel checked, even put on two new fronts. To no avail. Any help?