AUTOMATIC PARKING BRAKE FAILURE--BRAKE ENGAGED WHILE MOTORHOME IN MOTION, CAUSING BRAKE PADS AND DRUM TO SEVERLY OVERHEAT, RUINING COMPONENTS AND MAKING PARKING BRAKE INOPERATIVE. APPARENTLY, A PRESSURE SENSING SWITCH BEGAN LEAKING FLUID, WHICH CAUSED THE BRAKES TO ENGAGE WHILE MY WIFE WAS DRIVING DOWN THE HIGHWAY. AT THE FIRST AVAILABLE GM DEALERSHIP, THEY DIAGNOSED THE FAILED PRESSURE SWITCH, BUT WERE UNABLE TO REPLACE IT. THEY DISCONNECTED THE PARKING BRAKE SYSTEM, BUT TOLD MY WIFE THAT THE UNIT WAS SAFE TO OPERATE, THAT THE TRANSMISSION WOULD HOLD THE VEHICLE WHEN PLACED IN PARK. SHE FOUND OUT THAT THIS WAS FALSE WHEN SHE STOPPED THE MOTORHOME AND AS SHE WAS LEAVING IT, IT BEGAN TO ROLL. PLEASE RE-OPEN PE99-006. MY DEALER TOLD ME THAT GMC HAD A LOT OF PROBLEMS WITH THIS "NEW" PARKING BRAKE SYSTEM AND QUICKLY DISCONTINUED USING IT AND REVERTED TO THEIR "OLD" SYSTEM.