The original design shown here implemented a 21-position system of engaging, or locking the side and spider gears. The side gear (A) had a different number of engaging points than gear teeth. Therefore, when the clutch gear (B) meshed with the differential case (C) and the side gear, the side gear would lock on whatever tooth was handy. This configuration would unevenly distribute the load between the teeth of the side gears and spider gears. While ARB has always used aerospace-quality materials, they realized that timing the engagement of the side gear, clutch gear, and case would increase the unit's strength by 30 to 40 percent. ARB has also modified the locking mechanism itself to reduce the number of moving parts, eliminating the piston (D). | 
So you ask, what is a "timed" gear? This is where it gets fun. The new timed unit implements a splined side gear. This means that the teeth on the side gear (A) and the number of side-gear engagement positions (B) are matched, or splined. The splines also match the engagement teeth in the clutch gear (C) and the flange cap (D). Comprende? When engaged, the contact surface of the spider gear (E) and side gears is maximized, they are in perfect alignment, and contact pressure is distributed equally throughout the contact area. |
Where does the air come from? An onboard ARB compressor supplies 85 psi to the seal-housing assembly (1) via a copper line (2). Air is then transferred internally into the flange cap (3), which pressurizes the galley (4), a sealed circular groove in the flange cap that the clutch gear (5) rides in. Under pressure, the clutch gear slides forward (to the left) and engages the side gear (6). This couples the side gear, clutch gear, and flange cap, virtually spooling the axles, thus locking the differential. | 
Due to the fact that stuff happens in the real world, ARB tests each application against the components to which it will be installed in a Destructive Testing Lab. For example: an 8-inch Toyota locker would be assembled into a Toyota differential. The axle is then put under a load until something other than the locker snaps. (That's the destructive part.) |
After surviving the Destructive Lab test, and prior to a full production run, the unit is subjected to the harsh wheelspin test. This spins the axle at a speed of 40 mph with a high-torque three-phase motor, simulating a condition of 100 percent wheelspin (i.e., one wheel spinning in the air and one on the ground). A computerized controller then repeatedly engages and disengages the unit. ARB highly advises against this type of engagement on the trail but wants to know that it can take it. Surviving this, the unit is then run through the engage/disengage cycle 20,000 times to ensure longevity of components. | 
If you thought things like the ARB air compressor were imported from a Third World plant, not here, mate. Each unit is assembled and tested in the Melbourne facility by one of ARB's 300 on-site employees. |
In ARB's research and development department, rather than receiving the manufacturer's specifications for design, ARB actually purchases each new model for direct hands-on development and assurance of precise fit and function. Having the vehicle on site also provides a great platform for fitting and testing other ARB products ranging from roof racks and bullbars to suspensions and ARB's new line of truck canopies. | 
Pallets of the finished product await shipment in from ARB's 10-acre Melbourne facility. |
If you don't know the ARB story, the company was started the way many user-based companies begin: With a vision, a good idea, a welder, and in the family garage. The garage was Tony Brown's, and the year was 1975. While on an overland expedition to Australia's Top End, Brown and his mates found themselves making repairs to numerous crumpled fenders and bent bullbars, damage caused by close encounters with kangaroos. Realizing the need for equipment built to survive the rigors of real-world use, upon returning to Melbourne, Brown converted his garage into a production shop and called it ARB, for Anthony Ronald Brown
In 1987, after a decade of research and development on new products, Brown's growing company purchased a patent for a goofy thing (we say that with tongue in cheek) called the Roberts Diff-Lock, a pneumatically operated locker. Designed by Tony Roberts in 1982, the Diff-Lock was only available for three vehicles: two Toyota applications and one Land Rover. Knowing that it had a good thing, ARB took the ball and ran with it, setting its sights on the international 4x4 markets. Now call the ARB Air Locker, ARB engineers quickly developed new applications, including the Dana 44, which they brought it to the States. An introductory article graced the pages of Four Wheeler in 1987. At the time, Air Lockers were only available through Reider Racing and 4Wheel Parts Wholesalers.
In 1989, Jim Jackson, former international rep for Warn Industries, launched ARB USA Inc., and brought the full line of ARB products to the United States. ARB USA's facility, based in Renton, Washington, now manages distribution to all of the Americas with distribution outlets in Mexico, Columbia, Puerto Rico, and all of South America
Today, ARB is Australia's largest manufacturer and distributor of 4x4 accessories and has expanded its line of Air Lockers to more than 100 applications. With products ranging from truck canopies and rooftop tents, to suspensions, bullbars, and, of course, the Air Locker, ARB distributes its wares to more than 80 countries around the globe.