Editors Note: A special report from our friends at ARB…
AIR LOCKER 101
There is no true 4WD without a locking differential. An Air Locker is needed to make effective use of all the traction available between the tires and the surface of which we are driving on. Air Lockers give you the ability to take advantage of the traction that is available by supplying drive to all wheels when needed but also by providing the flexibility of remaining open when not.
An ARB Air Locker can be engaged at any speed as long as both wheels are spinning at the same rate and your foot is off of the accelerator. Simply engage the compressor switch, then press the Air Locker switch. If one wheel is spinning faster than the other, “crash locking” will occur which can cause damage or premature wear to the internal gears. Best practice would be to ease off the throttle, then engage the Air Locker before attempting the obstacle.
When disengaging your Air Locker, always remember that the teeth of the locking mechanism cannot disengage while under torque. Even with the switch disengaged, you may need to release the torque on your axle by rolling your vehicle forward or backward slightly before the locking mechanism will unlock.
Air Lockers have no special requirements for lubricants; however, ARB does not suggest the use of oil that contains limited-slip additives as they can shorten the life of the Air Locker seals. Oil should be chosen based on the climate that you live in and the nature of how you use your vehicle.
After the first 1,500 miles of use, ARB recommends changing the differential oil and cleaning the axle breather. The Air Locker is larger in mass when compared to the factory differential, thus the fluid capacity of the axle will be different. Fill the axle with oil until the level is at the fill plug hole, manually rotate the differential several times, and then fill again until level with the filler plug hole. Overtime, the axle will naturally find its maximum capacity. After 30,000 miles of off-road use or 45,000 miles of highway only use replace the differential fluid.
Air Lockers will engage at around 70 PSI. For faster engagement, ARB recommends air pressure between 100 and 150 PSI. Each ARB Air Compressor will provide enough air pressure to engage two Air Lockers. Both the Compact CKSA and High Output CKMA compressors will provide 100 PSI. The Maximum Output CKMTA will provide 150 PSI. The pressure switch supplied with the CKMTA, #180901, can also be utilized on the CKSA and CKMA compressors for faster engagement.
Air Lockers and motorsports go hand in hand. Air Lockers continue to evolve due to the support of off-road racing. Air Lockers have been able to survive through some of the toughest off-road races, including the Ultra4 King of the Hammers; one of the most difficult and technical off-road races around. But this accolade was not enough to satisfy our engineers.
ARB redesigned the two most popular race application lockers that suited a Ford 9” housing. The Competition Edition Air Locker was developed: RD99CE (35-spline) and the RD249CE (40-spline). The new features consisted of ring-gear bolt locking tabs and a unique casting that improved the overall case strength by over 290 percent.
“The thing the people don’t realize about ARB, is that they have been developing the parts as our series and sport has grown… they keep evolving as the sport has evolved.”
Air Locker, the official locker of Ultra4 has won 8 King of the Hammers and 6 Every Man Challenge championships. These championships show that ARB’s extensive research, design, quality, and commitment is a true reflection of the Air Lockers success.
“They hold to the abuse that our cars provide… I can still put the hammer down and know that they are going to live at the end of the race.”
The two most common brands of Air actuated lockers are ARB and the Yukon Zip. Both essentially do the same thing but are manufactured by two different processes.
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