1. Raise and support the vehicle.
2. Remove the wheels and tires.
3. Remove the brake components from the axle.
4. Remove the differential housing cover and drain the lubricant.
   • When removing the differential housing cover, leave one of the top bolts loosely in place until all of the oil is drained from the housing. This will allow you to control the rate that the oil will flow from the housing.
5. Remove the cotter pin, axle hub nut retainer, axle hub nut, and washer.
6. Remove the hub to knuckle bolts and then remove the hub assembly (Fig. 1).
7. Remove the disc brake rotor shield from the bearing carrier.
8. Now you can remove the axle shafts from the axle.
   • Be careful not to damage the axle shaft oil seals located in the differential assembly.
9. Remove both of the differential bearing caps.
   • Note the installation reference letters stamped on the bearing caps and housing machined sealing surface. These must be re-assembled exactly as removed.
10. Mount the differential spreader to the differential housing.
11. Separate the housing enough to remove the case from the housing. Measure the distance with a dial indicator.
    • Caution: Do not spread the housing more than 0.38 mm (0.015") to prevent damage.
12. Remove the differential carrier (Fig. 2).
    • When fitting an ARB Air Locker, a replacement bearing and shim pack supplied with the kit is used on the right hand side, but the original bearing and standard shims are used on the left hand (crown wheel) side.
13. Remove old bearings and shims from the differential carrier and identify left and right. Assess condition of bearings and shims and replace as necessary, remembering that only one bearing and shim pack will be re-used. Note that the shims on the crown wheel side may need to be changed to achieve correct backlash.
14. Remove the ring gear from the old differential carrier.

1. Fit the ring gear to your new ARB Air Locker differential carrier (Fig. 3).
   • Note: Heat the ring gear in hot water or in an oven to 175-212 degrees fahrenheit to facilitate assembly, ensuring the mating surfaces are clean before assembly.
2. Torque ring gear bolts to vehicle makers specifications using Loctite 290 on threads before tightening.
3. Mark the differential housing for a convenient hole location for the brass bulkhead fitting. While this location is not critical, the hole should be in the upper part of the differential housing toward the left hand side of the vehicle.
   • This will allow the plastic air line to be run over the top of the axle housing, and provide clearance for the bulkhead fitting and copper tube on the inside of the differential housing from the differential.
4. Drill a 7/16" diameter hole and tap a 1/4" NPT thread. Use cloth to protect the pinion gear and pinion bearings from swarf.
5. The differential may now be trial assembled into the differential housing. Re-install the ring gear side as per a standard differential carrier. On the air inlet side the procedure is: bearing inner, bearing outer, O-rings, seal housing, adjusting shims and the 2.5mm spacer washer. Assemble the differential carrier as above and as shown in Figure 5, but do not seal O-rings at this stage.
6. Set backlash approximately, but do not set bearing preload. Place the differential carrier assembly into the differential housing with the seal housing tube protruding straight out.
7. Select the non-ring gear side bearing cap and measure the hole location for the seal housing tube. Drill the bearing cap with a 1/4" bit for the seal housing tube (Fig. 6).
   • Note: Makes sure backlash is within +/- 0.010" of the correct tolerance to ensure that the seal housing tube hole location is correct.
8. Bend the seal housing tube to protrude through the tapped hole for the bulkhead fitting in the differential housing, ensuring that there is ample clearance from the differential carrier and ring gear. Mark the tube at a point flush with the outside of the housing.
9. Remove the differential carrier from the differential housing. Remove the seal housing, cut the tube with a tube cutter as marked, deburr and clean.
10. Clean all parts of the differential assembly. Assemble the differential carrier as directed in step #5, now fitting seal housing with O-rings (Fig. 7).
    • Lubricate O-rings with oil prior to assembly (Fig. 4).
11. Set the differential carrier preload and backlash in accordance with vehicle manufacturer's recommendations.
    • Note: New shims have been provided in .003", .005", .010", and .030". Original shims are also available in these sizes.
12. Install the bearing caps and torque to vehicle manufacturer's specifications (Fig. 8).
13. Screw the lower compression nut into the bulkhead body. Screw the bulkhead body into the tapped hole from the OUTSIDE of the housing, feeding the tubing up through the inside.
    • Note: To obtain an oil tight seal, use a thread sealant on the external thread of the bulkhead body.
14. Slide the 3/16" (or 1/8") ferrule over the copper coated bundy tubing. Screw in the central compression nut (making sure that the end with the thread undercut is down) and torque up, ensuring that the ferrule is tight on the tube.
    • Refer to the Compressor Installation Instructions for the correct procedure for fitting the blue plastic tubing using the remaining bulkhead fitting components.
15. Install the differential cover on the differential housing using a new gasket and sealant.
    • Be sure to clean the old sealant from the differential housing and differential cover mating surfaces prior to re-assembly of the differential cover.
    • Take care not to over tighten the screws as this may cause the differential cover to distort.
16. Clean the axle shafts and apply a thin film of wheel bearing grease to the shaft splines, seal contact surface, and hub bore. Slide the axle shafts into the housing and differential side gears.
    • Use care to prevent damage to the axle shaft bearings and oil seals located in the axle housing.
17. Refill the axle housing with good quality differential oil, referring to the manufacturers' specifications for the oil type and quantity.
    • Although the Air Locker does not require any special gear oil, ARB recommends using a limited slip differential oil to maximize the life of all differential components.
18. Install the brake dust shield and hub assembly to the knuckle using existing knuckle bolts.
19. Install the washer, axle hub nut, axle hub nut retainer and a new cotter pin.
20. Install brake components to the axle.
21. Install wheels and tires.

I've learned an easy way to remove the hub assembly from the steering knuckle. First, remove the cotter pin, axle hub nut retainer, axle hub nut, and washer. Next, back the knuckle bolts out approximately 1/4" with a 12-point 1/2" socket. Leaving the socket on one of bolts, tap on the socket with a hammer until the head of the bolt is once again flush with the back of the steering knuckle. The socket will protect the head of the bolt from damage from the hammer. Repeat this process with the other three knuckle bolts, and then back the bolts out another 1/4" and start the process over again. Soon the hub assembly will be free of the steering knuckle.

Here you see the front axle housing after the axle shafts, differential carrier, and ring gear have been removed. This is a good time to inspect your ring and pinion gears for any signs of worn or chipped teeth. If these conditions exist, they must be replaced prior to re-assembly.

When fitting the ring gear to your new ARB Air Locker differential carrier, be sure not to damage the bolt threads. The use of Loctite 290 on the threads will ensure a tight fit for years to come.

A high-quality lubricant such as "Sil-Glyde" should be used on the O-rings to assure longevity.

When fitting the ARB Air Locker to your differential housing, the stock shim setup on the ring gear side of the differential assembly will usually be reused.

Instead of drilling a 1/4" hole in the bearing cap for the copper seal housing tube, the experts at Moab Off Road have an alternative method. Here, Steve Nantz uses a die grinder to cut a notch in the bearing cap. (NOTE: Using the "notch" technique can jeopardize structural integrity of the bearing cap if done incorrectly. ARB recommends drilling a 1/4" hole for most applications.)

With the seal housing in place, the bearing cap fits easily around the copper seal housing tube (Dana 35 axle shown).

This is a properly installed ARB Air Locker in a Dana 30 axle.