The term "four wheel drive" can be very deceiving when referring to a vehicle?s drivetrain. One would normally assume that all four wheels on the vehicle receive driving force from the axles, however this is not always the case. Most "four wheel drive" vehicles come from the factory with open differentials that only deliver driving force to two of the wheels, one on each axle, when the vehicle encounters low-traction terrain. To further complicate things, the two wheels that receive power are the ones with the least amount of traction. This means that your 4X4 will only be driving on two wheels when traction is needed most. To fully understand how the four wheel drive system works, one must look at the axle?s differential. The differential lies in the vehicle?s axle housing and is designed to proportion the engines power to the axle shafts, which in turn drive the wheels. For a vehicle to turn, the outside wheels on each axle must turn at a faster rate than the inside wheels. The open differential allows the wheels to turn at different speeds, or independently of each other. This characteristic is desirable on pavement, but when you encounter a surface such as mud or snow, you may find yourself stuck, with only two wheels spinning uselessly, trying to gain traction.

This is where the ARB Air Locker comes into play. The Air Locker is designed to replace the open differential in your axle housing with a much stronger locking differential that will allow the driver to lock the axle shafts together when needed. When activated, the Air Locker will evenly distribute power to both wheels on the ARB-equipped axle, thus providing 100% traction instantly! Since the ARB Air Locker is driver-controlled, it can be engaged or disengaged at the driver?s discretion. Unlike automatic locking differentials, the ARB Air Locker does not have any adverse effects on the vehicle?s handling characteristics when driving on pavement. Automatic locking differentials force the wheels on the locker-equipped axle to turn at the same speed even when driving on high-traction surfaces. Since the wheels on an axle need to turn independently of each other when driving around a corner, some undesirable characteristics are common with automatic locking differentials:

• Chirping of tires when accelerating around corners
• Excessive free play, or slop, in the driveline
• Unstable handling characteristics on high-traction surfaces
• Difficulty steering and/or wheel hop during slow-speed turns
• Loud ratcheting noise from axle housing

The ARB Air Locker is controlled pneumatically from the driver?s seat of the vehicle. Once the dash mounted button is pushed, compressed air actuates a piston inside the ARB differential which engages a locking gear, instantly locking the differential and sending power to both wheels?all within one tenth of a second! Another push of the dash mounted button bleeds the air through the solenoid valve allowing small heavy duty coil springs in the ARB differential to release the locking ring. With the ARB differential disengaged, the axle shafts are unlocked and the wheels are once again allowed to turn independently of each other.

Compressed air is supplied by an ARB air compressor which can be mounted in any convenient location underneath the hood of the vehicle. The 12-volt continuous-duty compressor features a die-cast aluminum tank, oil-less operation, and a carbon-impregnated piston ring, making the unit virtually maintenance free. Supplied with the ARB air compressor is a wiring harness that makes installation a snap. A relay and pressure switch, air lines and fittings, industrial grade control switches, and all the necessary mounting hardware are also included with the compressor.

ARB offers a tire inflation kit (Part # PUKT) to integrate directly into the ARB air compressor system. Included with the kit is an air hose with a quick-disconnect air chuck, a high-quality VDO air pressure gauge, and all the necessary hardware required to install the kit to your ARB air compressor. When equipped with the tire inflation kit, the ARB air compressor is capable of inflating a 33x12.50 tire from 15-32 p.s.i. in 4.5 minutes.

Also available from ARB is a portable version of their air compressor (Part # RDCP). With the same specifications as the underhood compressor, the portable unit is ideal for inflating tires. The portable compressor comes with a quick-disconnect fitting for hands-free tire inflation, a high-quality VDO pressure gauge, quick-disconnect battery terminals, and is enclosed in a durable case for easy transportation.