Here's the scoop on lockers or all I've found. Only the USMC M813s had the Detroits. They have peculiar habits and the USMC knew this so they put a decal or data plate on the dash or inside a door indicating that it had locking differentials. The chance of your bridge truck having them is minute at best. There won't be any tags on the axles themself indicating it has the Detroits. As a test you can jack up one of the rear axles and spin the tire, if the other one spins backwards, its not locking. Get yourself a 12 ton bottle jack for that beast. An 8 ton will lift it but will require much effort.