Air Locker

Q: What is an ARB Air Locker?

A: The ARB Air Locker is a replacement differential carrier that can either operate as a conventional differential, or lock both rear (or front) axle shafts together allowing maximum drive torque to be transmitted to both wheels. The locking function is controlled by the driver. Front axles can be locked when traversing slippery surfaces, giving maximum traction, then unlocked to regain full steering capability. As a safety feature, the front differential cannot be locked unless the rear differential has been first locked.

Q: What gear oil should I run with my ARB Air Locker

A: Any conventional or synthetic gear oil that is appropriate for your location and driving style. Stay away from anything that says “For Limit-Slip Diffs” or “Friction Modifiers”

Q: Gear oil is pumping out the top of my solenoid. What can I do to fix this?

A: First, we need to explain why this happens. All axles have breather hoses or caps to allow the internal pressure to be equalized with the outside air pressure. Pressure can build up inside the axle housing if these passageways are blocked, sealed, or stuck closed. The gear oil leaks past the o-rings in an attempt to expand and escape the axle. Given enough heat, time, and pressure a siphon is established and the gear oil will draw itself out the nylon air line. When the locker is not engaged, the solenoid is off and the valve closes the air tank to the air line. The gear oil is being pushed out the exhaust port, but cannot get into the compressor tank.

To address the issue, check your breather lines. Clear any clogs, gunk, or buildup you find. Small spring caps are notorious for getting covered in mud and staying closed. Replace these silly factory pieces with a true breather hose and accordion style expansion tubes. The idea is to facilitate pressure equalization and eliminate pressure build up.

Q: Gear oil is misting out the top of my solenoid when I disengage the locker. Is this normal?

A: Yes, it is normal. The o-rings are bathed in gear oil inside the axle. When the locker is disengaged, all the air pressure in the airline and the locker is being released. When air passes the lubricated o-rings, moisture is picked up and carried out with the air. This results in the slight misting.

6 Responses to Air Locker

  1. shawn says:

    I have a RD114 and I have an air leak inside the locker. Air is coming out of the slots in the locker itself NOT the air collar. What is a fix for this ?

  2. Clay Morgan says:

    I’v had 3 different arb air lockers and every single one of them pumped oil up into my engine bay. No arb, my vent lines are not blocked, I’m not an idiot. I will buy almost any product made by arb, they make quality equipment. However, I will never purchase one of their air lockers again.

    • ARBMarket says:

      Hello Clay,

      The most common cause of oil pumping is axle pressurization for defective venting, but it’s not the only thing that will create this phenomenon. Without knowing what axle you are working with I can only give some general information on potential causes, but the following could be concerns.

      1. Damage to the sealing surface on the bearing journal where the o-rings ride. This can occur when the bearings are pressed on or if a tool such as a punch is used to tighten adjuster nuts and slips off knicking the sealing surface resulting in excessive clearance between the o-ring and the journal itself allowing oil to pass very easily.

      2. Adjuster nut damage. Again, incorrect tool for the job can deform the adjuster nut creating “risers” on the surface where the seal housing sits tight up against it causing the seal housing to sit at an angle instead of flat with 2 smooth machined surfaces. Using a file to smooth the risers and clean up the machined surface of the adjuster nut should put the seal housing back into alignment and stop the excessive oil pumping.

      3. Lack of preload on the carrier bearings. A potential issue on dana type axles if the bearing preload is non existent (diff pretty much falls out one the cap bolts are removed) then the diff will move around under load putting the journal into misalignment and again acting as a pump moving oil up the lines.

      4. Incorrect copper line routing. On many models the seal housing that holds the O-rings is designed to float on the end of the journal. If that float is impeded by an incorrectly routed copper line the seal housing can “wind up” as you drive and become lifted and out of alignment as it pushes against the copper line. Correctly the line routing will resolve this issue.

      5. Bent axle housing. Badly tweaked housings cause all sorts of misalignment issues that can result in in pumping. Though not very common in most applications this can be the culprit in dana 35 and AMC 20 axles that are easily damaged.

      6. Incorrectly machined sealing surface on the locker. If the sealing surface has defects or excessive grooving from the machining process that can cause oil to work it’s way into the seal housing and up the line. In your case I doubt this is the cause since you’ve see the issue in 3 separate Air Lockers. Odds of faulty machining on 3 different units is virtually zero.

      We’d be happy to help you find the cause and get it corrected, but need more information on the axle you are working with and the part number diffs you’ve had a problem with. From there it’s often possible to determine the culprit with a few decent photographs of the seal housing are and surrounding parts once the assembly is out of the axle.

      Please contact our tech department at

  3. Dennis says:

    Hi there, first and foremost I have to congratulate the engineers at ARB for creating such a great product for our Trucks. I have 2010 FJ Cruiser 6/MT and recently I have Re-geared the Truck and at the same time we installed an Air Locker up front ARB Part#RD-121 and I must emphasize the system was installed by a professional Technician who has done it many times and knows what he is doing. After I received the Truck, I was amazed how fast the system comes online and activates the locking mechanism instantaneously, and at the same time unlocks it as soon as I don’t need it. I am sure the winch that I have installed some years ago will become useless. Once more thanks for the great product.

    P.S. I must say to the future customers, make sure you are getting the “GENUINE” product from ARB since there are some Knockoffs out there.

    Sincerely Dennis
    Riverside CA

  4. Richard p kennedy says:

    Just had one of your air lockers installed in a Dana 30 jeep. Installation went great changed the gear ratio too. Jeep now is a beast on the trails and I am on my way to Moab Easter Jeep Week for the 2015 event. Great locker will probably change the Detroit in back to an ARB . Great product. See you in Moab.
    Richard in Phoenix,AZ

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