WHILE DECELERATING FROM ABOUT 35 OR 40 MPH WHEN YOU APPLY THE BRAKES THEN COME TO COMPLETE STOP THE VEHICLE ON THE REAR END WILL START TO LOUDLY THUMP, IT STARTS OUT SLOWLY THUMPING AND BEGINS TO SPEED UP AND WHEN YOU START TO RELEASE THE BRAKE IT BEGINS TO SLOW DOWN AND STOP ONCE ONE BEGINS TO ACCELERATE. WE HAVE HAD THE ISSUE ONGOING FOR ABOUT 3 MONTHS NOW, IT STARTED ABOUT 2 OR 3 WEEKS AFTER WE GOT THE VEHICLE AND IT HAS BEEN IN THE SHOP ABOUT 6 TIMES. THE VEHICLE HAD ABOUT 2200 MILES ON IT AND THE DEALER SAID IT WAS A 'LIKE NEW' LOANER VEHICLE. THE MECHANICS SAID THEY THOUGHT IT WAS A EXHAUST, SOMETHING WITH THE REAR BRAKES, OR MAYBE A PANEL IN THE BACK OF THE VEHICLE, THEY HAVE TIGHTENED, AND REPLACED ALMOST THE ENTIRE REAR OF THE VEHICLE AND THE PROBLEM STILL PERSISTS. THEY CANNOT FIGURE OUT THE PROBLEM AND I AM AFRAID IT MIGHT BECOME A SAFETY HAZARD. THE DEALER HAS CALLED GMC AND THE DEALER SAID GMC WILL NOT DO ANYTHING FOR US. *JB
