TRAVELING ON THE INTERSTATE APROXIMATLEY 70 MPH, THE LEFT REAR TIRE TREAD SEPARATED. THIS RESULTED IN A LOSS OF CONTROL AND THE VEHICLE IMPACTED THE GUARD RAIL. AT THIS POINT THE ENGINE AND TRANSMISSION SEPARATED FROM THE CAR AS THE CAR CONTINUED TO SPIN DOWN THE ROAD. THE CAR CAME TO A REST AFTER APPROXIMATELY 3 SPINS, AND THE ENGINE CAME TO REST ON THE OPPOSITE SIDE OF THE 3 LANE INTERSTATE.