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 right 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 (Fig. 2).
5. The differential carrier 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 fit 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 crown wheel side bearing cap and torque to vehicle manufacturer's specifications.
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. Slide the axle shafts into the carrier (Fig. 8). Install the C-clips and withdraw the axle shafts (Fig. 9). Insert the cross shaft retaining pin and screw (Fig. 10).
16. Install the second bearing cap and torque up all bearing cap bolts to the vehicle manufacturer's specifications.
17. 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.
18. Refill axle housing with good quality differential oil, referring to the vehicle 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.
19. Install brake components to the axle.
20. Install wheels and tires.

Steve Nantz of Moab Off Road removes the open differential carrier from the rear axle of "Project ZJ".

With the axle shafts, differential carrier, and ring gear removed, the 7/16" hole can be drilled for the brass bulkhead fitting. If the pinion gear is not being upgraded at this time, a cloth should be used to protect the pinion gear and pinion bearings from swarf when drilling. It's also wise to cover the axle tubes at the same time.

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.

With the ARB Air Locker properly installed, and the preload and backlash set to manufacturer's recommendations, it's now time to re-insert the axle shafts in the axle housing.

To reinstall the rear axle shafts, first lubricate the bearing bores and seal lips with gear lubricant. Next, insert the axle shafts through the seals and bearings until they are visible in the "window" located on the ARB Air Locker differential. Now the C-clips can be installed on the ends of the axle shafts.

Once the C-clips are installed, withdraw the axle shafts and insert the cross shaft retaining pin. Align the hole in the shaft with the hole in the ARB Air Locker differential and install the lock screw.