ARB Air Locker

ARB lockers are designed to fit specific axle models and configurations. Some of the best ways to identify your axle are:

1. Check the Owner’s Manual

• Some vehicles list axle types and gear ratios in the specifications section.

• Look under “Drivetrain” or “Axle Information.”

• May show standard and optional axle ratios for your trim.

2. Check the Axle Tag

• Look on the differential cover bolts or axle tubes for a small metal tag.

• The tag will typically list:

  • Axle model (e.g., Dana 44, Ford 9”)

  • Gear ratio

  • Build date or serial number

3. Look for Casting Numbers

• Clean the axle housing and look for cast-in numbers.

• These can be cross-referenced to confirm axle type.

4. Check RPO Codes or VIN

• Found in the glove box, door jamb, or inside the hood.

• Google your RPO code or use a VIN decoder to look up the axle info.

5. Ask Your Local Dealership

• Call or visit your local dealer’s parts department.

• Give them your VIN, and they can tell you:

  • Exact axle model

  • Gear ratio

  • Whether it has a factory locker or limited slip

Knowing your exact gear ratio is critical because ARB lockers are sometimes split by gear ratio ranges (carrier breaks).To find your gear ratio:

1. Check The Owner’s Manual / Axle Tag / RPO Codes

• Best place to start.

• Look for numbers like 3.73, 4.10, 4.56, etc.

2. Open the Diff Cover

• Count the number of teeth on the ring gear and pinion gear.

  • Divide ring teeth by pinion teeth = gear ratio.

  • Example: 41 ÷ 11 = 3.73

Spline count determines which ARB locker fits your axle shafts.

How to check:

• Stock Axles: You may find spline count in the manual or dealer info.

• Aftermarket Axles: if unknown you’ll need to pull an axle shaft and physically count the splines.

ARB lockers are spline-specific, e.g.:

• Dana 30: 27-spline vs 30-spline

• Dana 44: 30-spline vs 33/35-spline (aftermarket)

Differentials are not one size fits all; there may be differences for the same application. Be sure to verify fitment before ordering.

Once you know:

• Axle model

• Gear ratio

• Spline count

• Axle position (front/rear)

👉 Use our ARB Air Locker Application Guide to find the correct part number.

If you’re unsure, it’s worth reaching out:

🛠️ ARB Technical Support

• ARB USA has great tech support for fitment help.

• They can walk you through identifying your axle and choosing the correct locker.

• 📧 Email: [email protected]

• 📞 Phone: +1 (619) 940-1769

• ⚙️ Open A Support Ticket here
  

🚗 Your Local Dealership

• Especially helpful if your vehicle is newer or has OEM optional axles.

• They can pull your build sheet using your VIN and confirm all drivetrain specs.

Your 4x4 has both a front and rear differential. A differential is designed to distribute power to either the left or right wheel on each axle.

Sending power to just one side of the vehicle allows the left and right wheels to spin at different speeds, which is essential for smooth onroad cornering.

By design, a differential will send power to the wheel with the least traction. Offroad, this can be a problem, if one wheel is in the air or on a slippery surface, the differential will only power that wheel. This often leaves you stuck when one wheel on the front axle and one on the rear lose traction, since the wheels with grip won’t receive any power.

We need a locker to make full use of all the traction available between our tires and the surface we’re driving on. Lockers let you take advantage of that traction by delivering power to all wheels.

For example, in 2WD mode, power goes to just one of the rear wheels, giving you 25% of the available drive. Switching to 4WD sends power to one of the front wheels as well, giving you 50%. This is where lockers make the difference, engaging the rear locker sends power to both rear wheels, and combined with one front wheel, delivers 75% of available drive. Engaging both the front and rear lockers sends equal power to all four wheels, giving you 100% of available drive.

We’ve explained the basics of how a standard differential works and why it’s useful on the road. However, when it comes to offroading, it can create problems on uneven or muddy terrain where one or more wheels may slip or even lift off the ground.

The best time to engage a diff locker is when driving over low traction surfaces, whether they’re slippery or uneven enough to cause wheel lift.

Locking the differential sends equal power to both wheels, so even if one is off the ground, the wheel with traction can push the vehicle forward and keep you moving down the trail.

The truth is, you can’t control the traction of the trail surface, but you can control the type of tires you use, your tire footprint (air pressure), and whether your tires are receiving power. All of these factors greatly increase your chances of finding and maintaining traction.

If there’s no traction on the surface, you can have all four wheels spinning with little to no forward progress. The first steps to improving traction are:

· A quality set of all-terrain or mud-terrain tires.
· Always adjusting tire pressure to match the terrain you’re driving on.
· Lowering tire pressure increases the contact patch with the ground, more tire on the surface means better load distribution and more grip. This is especially important when driving on sand, but also helps on rocky terrain where the tires can flex and mold around obstacles, improving traction.

The main benefit that an Air Locker has over an electronic-locker is its instant activation. By comparison to the majority of electronic lockers, an ARB Air Locker engages instantly and at any speed; furthermore, an ARB Air Locker has no operating speed limitations.

Being able to engage your locker ‘on the fly’ means you don’t need to lose your momentum before tackling an obstacle.