MY CAR WILL ROCK BACK AND FORTH VIOLENTLY WHILE DRIVING. NOTICE IT MORE AT HIGHER SPEEDS, SEEMS TO HAPPEN WHEN I TAKE MY FOOT OFF THE GAS PEDAL. IT'S PROGRESSIVELY GETTING WORSE AND I'M TERRIFIED OF HAVING A WRECK. HAVE TRIED NEW TIRES, TIRE ROTATIONS, ALIGNMENTS ETC.. I'VE BEEN TOLD IT MAY BE THE DIFFERENTIAL. *TR