THE AMBULANCE WAS DRIVING DOWN THE HIGHWAY WHEN THEY FELT A VIBRATION THEN HEARD A LOUD NOISE. THE CAB FILLED WITH SMOKE AND THEY LOST STEERING, BRAKES AND THE ENGINE SHUT OFF. ENGINE THEN CAUGHT ON FIRE. AFTER THE FIRE WAS PUT OUT, FOUND THAT THE TRANSFER CASE WAS IN PIECES. FOUND ENGINE HARNESS DAMAGE, BOTH DRIVESHAFTS, BRAKE AND FUEL LINES DAMAGED. AMBULANCE BOX AND TRUCK FLOOR BOARD DAMAGED.