DRIVER DRIVING DOWN FLAT HYWAY AND BRAKES STARTED SMOKING TRUCK STARTED ON FIRE, FIRE DEPTMENT WAS ABLE TO GET THE FIRE UNDER CONTROL BEFORE TOTAL LOSS OF TRUCK AND TRAILER, 36,000 DAMAGE TO TRUCK PLUS THE DAMAGE TO TRAILER CALLED IN HALDEX TECH REP DURING INVESTIGATION FOUND LEFT REAR HALDEX BRAKE CHAMBER FAILED WHICH RESULTED IN A LOSS OF AIR PRESSURE AND CAUSING THE BRAKES TO DRAG AT HYWAY SPEEDS CAUSING THE WHEEL END FIRE, BRAKE CHAMBER WAS LATER REMOVED AND DISARMED AND INSPECTED AND FOUND SPRING HAD BROKEN PUNCTURING THE AIR DIAPHRAGM CAUSING THE FIRE AND LOSS KNOWN DEFECT WITH THIS GOLD SEAL HALDEX BRAKE SPRING