I have a 1994 bronco with 4wd auto. I love the truck but repairs are killing me. The current problem im having is around 40 mph when accelerating i feel a heavy vibration but i let off and it seems to stop. I have a new transmission, new driveshaft, and a rebuilt rear end. Now the diffrental shop says its the axle shafts, and the axle shaft shop says its the differental. Im hoping the wheels are out of balance. Please help.