All Wheel Drive Automatic I GET A VIBRATION AT THE SPEED OF 140 KM. IT IS NOT WHEEL BALANCING PROBLEM, AS SOON I SLOW DOWN TO 130 THE VIBRATION GOES. ALSO THERE IS A GRINDING/ HUMMING NOISE VW DEALER SAYS THE VIBRATION IS DUE TO FAULTY REAR DIFFERENTIAL AND DIF IS DONE BUT STILL VIBRATION , AND I CHANGE THE GHEARBOX AND TANSFERBOX AND STILL THE SAME. APPRECIATE YOUR HELP IN ADVANCE