ARB Air Lockers Explained: Dana 44, Ford 8.8, AAM and GM 14-Bolt Applications

What Is an ARB Air Locker?

The ARB Air Locker is a driver-controlled selectable locking differential. During ordinary driving it operates like an open differential, allowing the left and right wheels to rotate at different speeds as the vehicle turns. When extra traction is needed, compressed air activates the internal locking mechanism and effectively couples both axle shafts together.

That means both wheels on the locked axle receive drive rather than allowing most of the usable torque to escape through a wheel that has lost traction.

Browse drivetrain components in Off-Road Canada's Differentials, Axles and Final Drive Gears collections when planning a complete axle build.

Selectable Locker vs Automatic Locker

Selectability is particularly valuable in a vehicle that sees both pavement and difficult trails. Drivers can leave the differential open when maximum differentiation is desirable and activate full lock only when conditions warrant it.

How an Air-Actuated Locker Works

An ARB Air Locker relies on compressed air supplied through an air line to the differential. When the dashboard switch is activated, a solenoid sends compressed air to the locker. Internal components move the locking mechanism into position so the side gears can no longer differentiate normally.

Switch the locker off and air pressure is released, allowing the locking mechanism to disengage and normal differential action to return.

What an installation typically needs

• The correctly specified ARB Air Locker for the axle.
• A compatible ARB air compressor.
• Solenoid and electrical switching hardware.
• Air line routed from the compressor to the differential housing.
• Correct carrier bearings, shims and installation hardware for the application.
• Proper ring-and-pinion backlash and bearing preload setup.

The Five Specifications You Must Check Before Ordering

1. Axle Model

A vehicle name alone is not enough. A Jeep, Ford, GM or Ram platform may have been offered with multiple axle assemblies depending on engine, trim, tow package, GVWR, model year or whether the axle has previously been swapped.

You need to identify the actual differential underneath the vehicle: for example, Dana 44, Ford 8.8, AAM 9.25/9.50 or GM 10.5-inch 14-bolt.

2. Axle Spline Count

Spline count describes the number of splines at the end of the axle shaft where it engages the differential side gear. A 30-spline locker cannot simply replace a 35-spline version unless the rest of the axle build is being changed accordingly.

More spline count is often associated with a larger or higher-capacity axle shaft, but spline count should primarily be treated as a fitment specification, not as a universal strength rating.

3. Carrier Break and Gear Ratio

Some axle families use different carrier offsets for different ranges of ring-and-pinion ratios. This is commonly called a carrier break.

That is why you may see two lockers that both say "Dana 44" and have the same spline count but one is listed for 3.73 and down while another is listed for 3.92 and up.

4. Full-Float vs Semi-Float Construction

Heavy-duty axle families can have substantially different designs. A GM 14-bolt full-float axle, for example, should not be treated as interchangeable with every axle that happens to carry a "14-bolt" description.

5. Specific Carrier and Ring-Gear Design

Some applications go beyond a simple numerical gear-ratio break. The AAM 9.25/9.50 product featured below is the RD254 low-speed-carrier version. That is a good example of why ordering strictly by ring-gear diameter or spline count can lead to the wrong part.

ARB Air Locker Application Comparison

These specifications should be used as a starting point only. Always verify the complete axle and ring-and-pinion configuration before purchasing or beginning installation.

Featured ARB Air Lockers

Why Axle Identification Matters So Much

One of the most common differential-shopping mistakes is using only the vehicle's year, make and model to identify a locker.

The original axle could vary with trim or equipment, and many older off-road vehicles have already undergone axle swaps, gear changes or upgraded axle-shaft installations.

Before ordering, verify as many of these as possible:

• Axle manufacturer and model.
• Ring-gear diameter.
• Front or rear axle position.
• Axle spline count.
• Current differential type.
• Current gear ratio.
• Carrier break.
• Full-float, semi-float or independent configuration where applicable.
• C-clip or non-C-clip design where applicable.
• Whether the axle has been swapped or previously modified.

Front Locker vs Rear Locker: Which Should You Install First?

There is no single answer for every vehicle. The ideal setup depends on drivetrain design, terrain, steering behaviour and how the vehicle is used.

Rear Locker

A rear locker is a popular traction upgrade because the rear axle carries substantial propulsion load and can provide a major improvement on climbs, cross-axle terrain, ledges and loose surfaces.

Front Locker

A front locker can deliver a substantial increase in technical off-road capability, especially when one front wheel becomes unloaded on rocks or uneven terrain. The trade-off is that a locked front differential can significantly increase steering effort and the vehicle's tendency to push straight ahead.

Front and Rear Lockers

A dual selectable-locker setup offers the greatest flexibility. The driver can run both differentials open, lock only the rear, or engage both when the obstacle demands maximum traction.

Selectability is particularly useful because a front locker does not need to remain engaged once the difficult portion of a trail is complete.

Why ARB Air Lockers Work So Well for Rock Crawling

Rock crawling often places a vehicle in situations where suspension articulation leaves one wheel with very little vertical load. An open differential can allow the unloaded wheel to spin while the tire with better traction receives insufficient usable torque.

Engaging a selectable locker removes normal differential action across that axle. This can help the vehicle crawl rather than relying on speed or wheelspin to clear an obstacle.

Advantages on technical terrain can include:

• Improved traction when a tire is partially or completely unloaded.
• More controlled climbing over ledges and rock faces.
• Reduced dependence on momentum.
• Better performance through deep cross-axle articulation.
• Driver control over exactly when the axle is locked.
• The ability to disengage the locker when tighter steering is required.

Lockers are useful outside rock crawling as well. Deep mud, loose climbs, snow, washed-out trail sections and uneven forest access roads can all create situations where additional traction across an axle becomes valuable.

Do ARB Air Lockers Require a Compressor?

Yes. An ARB Air Locker needs a compatible compressed-air source to actuate its locking mechanism.

The correct compressor setup depends on how many lockers are being operated and whether you also want the compressor for additional functions such as tire inflation.

A typical system consists of:

1. ARB compressor.
2. Wiring harness and switches.
3. Air Locker solenoid.
4. Air line running toward the axle.
5. Bulkhead fitting entering the differential housing.
6. Internal seal and activation components inside the differential.

Compressor placement should keep the equipment protected while allowing adequate airflow and service access. Wiring must also be properly fused and routed away from heat, moving components and potential abrasion points.

Air-Line Routing: Small Component, Big Consequences

The air line is one of the defining differences between an air locker and a purely mechanical locker. It needs to survive an environment filled with heat, suspension travel, mud, rocks and moving drivetrain components.

Good routing practices include:

• Keep the line away from exhaust components and other high-heat sources.
• Avoid driveshafts, steering components and rotating parts.
• Leave sufficient slack for full axle articulation and suspension travel.
• Prevent sharp bends, crushing and abrasion.
• Secure the line at sensible intervals.
• Protect exposed areas where rocks or trail debris could strike the line.

After installation, the pneumatic system should be checked for air leakage and the locker should be tested for consistent engagement and disengagement.

Lockers, Bigger Tires and Increased Drivetrain Stress

A locker improves traction, but additional traction also means the drivetrain can transmit substantially more torque before a tire slips.

That makes the rest of the axle assembly increasingly important, particularly on a heavily modified 4x4 running large tires, deep gearing and aggressive terrain.

Components that can experience greater load include:

• Axle shafts.
• Front axle U-joints or CV joints.
• Ring-and-pinion gears.
• Driveshafts.
• Transfer-case components.
• Wheel hubs and bearings.

For more demanding builds, explore Off-Road Canada's Axles and Final Drive Gears categories when planning the entire drivetrain around increased traction.

Should You Regear at the Same Time as Installing an Air Locker?

If larger tires have already made the vehicle feel sluggish or reduced crawl control, installing a locker can be a logical time to consider a regear.

Both jobs require significant differential disassembly, and a locker installation already involves removing the carrier and correctly resetting the differential. Combining the projects can make sense when the vehicle needs both upgrades.

Regearing can also become necessary when moving between carrier-break configurations. Depending on the axle, the chosen locker, ring-and-pinion ratio and availability of thick gears may all interact.

Choosing an ARB Air Locker: Quick Checklist

1. Identify the exact axle. Do not rely exclusively on the vehicle model.
2. Confirm axle position. Determine whether you are locking the front or rear.
3. Confirm spline count. Count or verify the axle-shaft spline specification.
4. Check the existing gear ratio.
5. Identify the carrier break or carrier style.
6. Verify full-float/semi-float and other axle architecture.
7. Decide whether you are regearing at the same time.
8. Select a suitable compressor.
9. Plan compressor, wiring and air-line placement.
10. Have the ring-and-pinion professionally set up if you do not have differential-building experience.

Which of These ARB Air Lockers Is Right for Your Build?

Frequently Asked Questions About ARB Air Lockers

Related Drivetrain Parts for an Air Locker Build