While backing down grade and cutting the wheels hard (but not necessarily all the way) the front end makes and loud noise and feels like somthing's slipping or dislocating. Feels violent, car shakes and this can be heard inside and outside the car. Been to the dealer five times they couldn't duplicate the noise. Replaced some parts. At one point they thought that because they rotated my rear tires to the front during service, leaving the 55s on the front was causing the noise. Well putting the 45s back on the front didn't correct anything. Finally got them to come over to my house, because it happens everytime I back out of my driveway and they determined it was the tire skipping because of its width. They say it's normal and won't cause and damage. Car handles an brakes fine. Anyone experiencing this and believe the tires are causing this?