ACADIA WAS TRAVELING AT 55 MPH WHEN HEARD/FELT A POP/BUMP. STEERING WHEEL STARTED SPINNING TO LEFT THEN RIGHT. STEERING WHEEL STRAIGHTENED OUT. WHILE STEERING WHEEL WAS STILL FACING STRAIGHT, THE CAR STARTED VEERING SHARPLY TO THE RIGHT. THE ACADIA HIT A CULVER THEN FLIPPED 4 TIMES, COMING TO A STOP OVER 160 FEET FROM WHERE IT LEFT THE ROAD