VEHICLE INVOLVED IN WHEEL END FIRE THAT DESTROYED THE ATTACHED TRAILER AND LOAD. DAMAGE TO TRACTOR WAS CONTAINED TO THE REAR CHASSIS AND BACKSIDE OF THE CAB. VEHICLE WAS IN MOTION ON INTERSTATE HIGHWAY WHEN THE DRIVER SAW SMOKE COMING FROM THE TRACTOR DRIVE WHEELS. TIRE BLEW SOON AFTER AND FIRE COULD NOT BE EXTINGUISHED BY ON BOARD FIRE EXTINGUISHER. THE FIRE PREVENTED ACCESS TO FIFTH WHEEL RELEASE. DRIVER WAS UNABLE TO SEPARATE TRAILER FROM TRACTOR TO PREVENT FURTHER DAMAGE AND LOAD LOSS. TOTAL DAMAGES IN EXCESS OF $250K FORMAL FIRE INVESTIGATION AT STORAGE LOT AND SUBSEQUENT LAB INSPECTIONS CONCLUDED THAT A HALDEX 3030 GOLDSEAL CHAMBER TO BE THE ROOT CAUSE. THE PARKING SPRING HAD FAILED AND PUNCTURED PARKING SIDE DIAPHRAGM. THE SUBSEQUENT LEAK CAUSED PARKING BRAKES TO PARTIALLY APPLY WHILE VEHICLE WAS MOVING. THE PRIVATE FIRE INVESTIGATION FIRM HIRED BY THE FLEET PROVIDED X-RAYS SHOWING THE SPRING FAILURE PRIOR TO DISASSEMBLY. THIS FLEET HAS DOCUMENTED NUMEROUS HALDEX GOLDSEAL 3030 CHAMBER FAILURES ON ITS OTHER SAME YEAR,MAKE MODEL TRACTORS. FAILURES ARE OCCURRING AT ABNORMALLY HIGH RATES AND WITHIN THE FIRST 2 YEARS FROM DATE OF IN-SERVICE.