I WAS DRIVING MY 2004 SUBARU IMPREZA OUTBACK SPORT WHEN I HAD A FLAT TIRE (RIGHT REAR). I CHANGED THE TIRE, USING THE "DONUT" IN THE CAR. I DROVE ANOTHER 25 MILES NO FASTER THAN 40 MPH, AND US. SLOWER. THEN A DRIVER BEHIND ME FLASHED HER LIGHTS SIGNALING ME TO STOP. I STOPPED AND LEARNED MY CAR WAS BURNING UNDERNEATH, NEAR THE BACK. WHEN I HAD THE CAR LOOKED AT, I FOUND THAT THE REAR DIFFERENTIAL WAS BADLY DAMAGED. IN THE OWNER'S MANUAL, PERSONS WITH AUTOMATIC TRANSMISSIONS ARE INSTRUCTED TO USE A SWITCH TO TURN OFF THE AWD WHEN DRIVING ON THE "DONUT." OTHERWISE, DAMAGE TO THE DIFFERENTIAL IS LIKELY. HOWEVER, NO SUCH SWITCH EXISTS FOR CARS WITH MANUAL TRANSMISSIONS, WHICH I HAVE. I FOLLOWED THE INSTRUCTIONS, NOT GOING MORE THAN 50 MPH OR MORE THAN 50 MILES ON THE DONUT. BUT I DID EXTENSIVE DAMAGE ANYWAY, AND THE FIRE (WHICH WAS CAUSED BY THE HEAT OF THE DIFFERENTIAL SETTING THE UNDERCOATING ON FIRE) COULD HAVE BEEN DANGEROUS. *TR