Installing ARB Air Lockers in Dana 44 Axles: A Comprehensive Guide

The Dana 44 is one of the most popular and durable axle platforms found in Jeep Wranglers, Ford Broncos, and many full-size trucks. While capable in stock form, serious off-roaders often seek more traction control. Adding an ARB Air Locker transforms your Dana 44 into a true off-road weapon, providing on-demand full lockup without compromising daily driving manners. This guide covers every phase of the installation – from tool selection and preparation to final testing – ensuring you get reliable, long-lasting performance.

ARB Air Lockers have been the gold standard for selectable locking differentials for decades. Unlike automatic lockers that engage unpredictably, air lockers let you choose when to lock and unlock. When engaged, they physically connect both axle shafts, forcing both wheels to turn together. This is invaluable in mud, rock, sand, or any low-traction situation. The Dana 44 is well-suited for this upgrade thanks to its robust carrier design and widespread aftermarket support.

Before diving in, understand that this is a major driveline modification. If you are not comfortable working with ring and pinion backlash, bearing preload, and air systems, have the locker professionally set up. However, with careful attention and the right tools, a skilled DIY mechanic can achieve excellent results.

Understanding ARB Air Lockers

An ARB Air Locker replaces the standard differential carrier. It contains a locking mechanism that slides a dog clutch to engage the side gears to the carrier, locking the axle. The mechanism is actuated by compressed air (typically 90–110 psi) delivered through a hose routed into the axle housing. When air pressure is released, a spring disengages the lock, returning the differential to open operation.

This design offers several advantages over electric lockers: air actuation is smooth and instantaneous, the mechanism is simple and robust, and the compressor can also be used for other accessories like tire inflation. The downside is that it requires an external air compressor and a small air tank (or just a storage tank). ARB sells complete kits with the locker, compressor, and all necessary fittings.

Tools and Materials Needed

Proper preparation minimizes downtime and mistakes. For a Dana 44 installation, you will need:

  • ARB Air Locker kit specific to Dana 44 (verify axle spline count: standard Dana 44 uses 30 spline, some variations use 19 or 30)
  • Air compressor kit from ARB (recommended RDK117 for medium vehicles or CKSA12 for larger air demand)
  • Socket set up to 1-inch (includes 1/2-inch drive for hub nuts)
  • Torque wrench (inch-pound and foot-pound) – critical for bearing caps and carrier bolts
  • Dial indicator with magnetic base for measuring backlash and runout
  • Bearing puller and press for removing/replacing carrier bearings
  • Differential cover gasket (or RTV silicone)
  • Gear oil: typically 80W-90 or 75W-140 for Dana 44, capacity 1.5–2 quarts
  • Air line (supplied with locker) plus extra 1/4-inch nylon tubing for routing
  • Drill bit set for creating passages in the axle housing (for air line)
  • Thread locking compound (Loctite 242 medium strength)
  • Safety gear: gloves, safety glasses, jack stands (2-ton capacity minimum)
  • Shop rags and degreaser
  • Transmission drain pan for old fluid

If you are reusing your original ring and pinion gear, you must also have the correct shims and bearings for the carrier. ARB lockers come with their own bearings and possibly new shims. Check the kit contents against the ARB installation manual before starting.

Pre-Installation Preparation

Axle Identification and Setup

Identify your Dana 44 model. Common variations include factory LSD or open differential. The install procedure is similar, but if you have a factory limited slip, you must remove it completely. Also note the gear ratio – the ARB locker fits all ratios but may require specific carrier shims. Measure your original carrier shim pack thickness to use as a starting point.

Clean Work Environment

A clean workspace is vital. Any debris in the differential will cause rapid wear. Lay out a clean tarp, use magnetic trays for hardware, and have a container to store old parts. Consider working on a solid concrete floor with good lighting.

Air Compressor Location

Before touching the axle, decide where to mount the ARB compressor. Common locations are under the hood (on the fender well or firewall), inside the engine bay, or under the vehicle. Ensure it is protected from water and mud, has access to a power source (relay and fused wire), and is near enough to the axle for the air line. Also consider running a small air tank (ARB sells 1-liter and 2-liter tanks) to buffer pressure for quick locker engagement.

Step-by-Step Installation Process

1. Vehicle Preparation and Differential Disassembly

Jack up the vehicle securely on both sides and place on jack stands. Remove both rear wheels (if working on a rear Dana 44) or front wheels (for front axles, also remove hubs and axle shafts). Drain differential fluid by removing the lower fill plug or cover. Mark the driveshaft and pinion yoke for realignment later. Remove the driveshaft(s).

Unbolt the differential cover – be ready for residual oil. Clean the housing thoroughly. Inspect the ring gear and pinion for wear. Mark the position of the bearing cap and adjuster nuts (if applicable). For a Dana 44, the carrier is held by two bearing caps that must be removed carefully. Record the number of shims on each side.

Remove the carrier and ring gear assembly. Separate the ring gear from the old carrier using a press or pry bar. Keep the ring gear bolts in order – they are specific to the ring gear. Clean the ring gear and inspect it.

2. Install Ring Gear on ARB Locker

Place the ARB locker on a clean surface. Install the ring gear onto the locker flange using new bolts (often provided with the locker). Apply thread locking compound and torque to manufacturer spec – typically 45–55 ft-lbs for Dana 44. Use a crisscross pattern. Check runout of the ring gear with a dial indicator – runout should be less than 0.002 inches. If not, clean the mating surfaces or check for burrs.

3. Install Carrier Bearings and Shims

Press the new carrier bearings onto the ARB locker. Some lockers come with different bearing sizes – ensure correct orientation. Transfer the shim packs from the original carrier or use new shims. The total shim thickness on each side determines the backlash and carrier bearing preload. Use the original shim thickness as a starting point but be prepared to adjust. Install the carrier into the housing temporarily to check backlash. If backlash is outside spec (typically 0.005–0.008 inches), adjust shims.

This step often requires trial and error. A dial indicator on the ring gear teeth while rotating the pinion helps set backlash. Do not skip this – improper backlash leads to noise and gear failure.

4. Install Air Line into Axle Housing

ARB supplies a drill guide and tap for creating a port in the axle housing. Usually, you drill into the top or side of the housing near the carrier area. Follow the template exactly – the hole must be clean and deburred. Insert the supplied bulkhead fitting and seal with thread sealant. Run the air line from the fitting out of the housing, ensuring it does not interfere with the ring gear or carrier. Secure the air line inside the axle with clamps or zip ties.

Route the exterior portion of the air line along the axle tube, avoiding hot exhaust, sharp edges, and suspension components. Use protective loom or split tubing. Connect the other end to the compressor’s air output. Include a one-way check valve near the locker to prevent backflow and moisture issues.

5. Install the Locker into the Axle

With the carrier bearings and ring gear installed, place the ARB locker into the housing. Ensure the air line is aligned with the port – do not kink it. Install the bearing caps and tighten to spec (typically 60–80 ft-lbs for Dana 44). Recheck backlash and gear pattern after torquing caps. If the pattern is off, adjust shims again. This is the most critical part of the installation – if you are uncertain, consult a professional gear setup guide or Dana’s service manual.

6. Reassemble Axle Shafts and Hubs

Install axle shafts per standard procedure. For Dana 44 fronts (if not a full-floating rear), ensure the axle shafts engage the locker’s side gears. Use new axle seals if removed. Reinstall brake components, hub bearings, and locking hubs if applicable.

7. Install Differential Cover and Fill with Fluid

Clean the housing and cover mating surfaces. Apply a thin bead of RTV (or install gasket) and bolt the cover to spec. Fill with recommended gear oil – ARB recommends conventional gear oil (not synthetic) for initial break-in of the locker. Do not use limited-slip additives – they can contaminate the air system. Use standard 80W-90 for most climates.

Check for leaks around the air line fitting inside and outside the housing. Add gear oil until it weeps from the fill hole.

8. Mount and Wire the Air Compressor

Mount the ARB compressor securely. Connect it to a switched 12V power source through a relay and 20-amp fuse. Use the wiring harness provided. Ground to clean chassis. The compressor should only run when the ignition is on. Install the red control switch (ARB style) in the cab.

Plumb the compressor output to a T-fitting: one branch goes to the locker, the other to an air storage tank or tire inflation hose. Install a pressure switch to keep the compressor from overheating. ARB compressors have a built-in thermal overload.

9. Air Line Routing and Connections

Connect the air line from the axle to the compressor output. Use push-to-connect fittings. Check for leaks using soapy water. The locker seal is also tested: pressurize the system to 100 psi and listen for hissing. If no leaks, depressurize and repeat with the locker engaged (by applying low pressure to the line).

10. Test the Locker Operation

With the vehicle on stands, start the engine, turn on the compressor, and wait for it to build pressure. Flip the dash switch – you should hear a distinct click as the locker engages. Rotate the wheels manually – with locker engaged, both wheels should turn together. Disengage – wheels should rotate independently. Test multiple times. Also, drive a short distance on a loose surface to verify engagement and disengagement under load.

Common Mistakes to Avoid

  • Improper backlash setup: using old shims without rechecking gear pattern leads to whine and rapid wear.
  • Incorrect air line routing: pinched or chafed lines cause leaks and locker failure. Use grommets at all passes through sheet metal.
  • Over-tightening air fittings: poly fittings can crack; tighten hand-tight plus 1/4 turn.
  • Neglecting to use thread locker on ring gear bolts: these bolts can loosen, causing catastrophic damage.
  • Using synthetic gear oil for break-in: ARB recommends conventional oil for the first 500 miles to allow proper seating. Switch to synthetic later if desired.
  • Insufficient compressor capacity: small compressors may not provide enough cycles and can overheat. Use the correct size ARB compressor.
  • Not installing a check valve near the locker: without it, oil can migrate into the air line, causing sluggish operation.

Maintenance Tips for ARB Air Lockers

Once installed, follow these guidelines to maximize reliability:

  • Inspect air lines annually for cracks, abrasion, or kinks. Replace any suspicious sections immediately.
  • Change differential fluid every 30,000 miles or after heavy use. Use good quality conventional or synthetic gear oil (but break-in on conventional).
  • Test locker operation every few months by engaging/disengaging on a gravel road. Listen for unusual sounds.
  • Check compressor mounts and wiring for corrosion or looseness. ARB compressors are durable but need clean connections.
  • Drain air tank regularly if you have one, to remove moisture that could freeze in winter or clog the locker.
  • Torque bearing cap bolts after first 500 miles – they can settle.

For long-term storage, engage the locker every few weeks to keep seals lubricated. If you will not use the vehicle for months, store in a dry place or apply anti-rust spray inside the differential through the fill hole.

Conclusion

Installing an ARB Air Locker in a Dana 44 axle is one of the most effective upgrades for off-road capability. It provides instant, driver-controlled traction without affecting on-road manners. The installation requires mechanical skill, precision, and patience, but the results are well worth the effort. By carefully following this guide and adhering to ARB’s specifications, you can enjoy years of reliable performance on any terrain.

For additional reference, check the ARB Air Locker product page for kit numbers and updates. Always cross-reference your Dana 44 variant with your locker’s requirements. With proper installation, your vehicle will be ready for the toughest trails.