HOW THE ARB AIR LOCKER WORKS An ARB AIR LOCKER is a unique type of replacement differential center which allows the driver to choose between a conventional or a fully locked differential by operating a rocker switch on the dashboard. The ability to manually engage and disengage means that the ARB AIR LOCKER can be fitted to the front diff, as well as the rear diff, without affecting the steering when disengaged. When the ARB AIR LOCKER is engaged the air solenoid valve (located on the compressor) opens, and compressed air is fed down the plastic feed line to a bulkhead fitting installed in the differential housing. A steel tube runs from the bulkhead fitting to an air seal housing which is locked in position on the bearing journal over a small air inlet hole in the differential. Compressed air is thus injected into the ARB AIR LOCKER while it is rotating. The compressed air activates an annular piston built into the differential and completely-locks the differential via a large locking gear. When the dashboard mounted switch is turned off, the compressed air is exhausted through the solenoid valve, and small heavy duty coil springs in the differential release the locking ring. Now the differential acts as a normal "open" differential. The compressor kit, when supplied, is located in any convenient position in the engine compartment or, alternatively, inside the cabin of the vehicle. A pressure switch is incorporated which turns the compressor off when the tank pressure reaches a preset maximum, and on if the pressure drops to the preset minimum. The compressor is connected into the ignition circuit, via an isolating switch (which is supplied in the compressor kit,) so that it can be actuated when use of the ARB AIR LOCKER is engaged, or, the pump-up kit is required. When ARB AIR LOCKERS are installed in both the front and rear differentials a unique feature in the wiring prevents the front ARB AIR LOCKER from being engaged unless the rear ARB AIR LOCKER is engaged.