ARB air lockers have proven to be strong, reliable, and quick to actuate on demand. We have used a number of them over the years with great success. Generally, the seals that contain the locking air pressure inside will last many, many years. This is assuming that your gear lube stays relatively clean, you don't pollute it with metal debris from abnormal axle wear or metal bits from carnage, and that they aren't damaged by careless installation practices when the unit is originally installed or while the gears are being set up. That being said, you should typically only need to replace ARB seals if they become damaged for any of these reasons.
We were experiencing some air leakage inside one of our Dana 60 ARB lockers, so decided to tear into the differential to take a look. We found that one of the two Viton O-rings under the seal housing had gotten twisted upon installation. After more than a decade of hard use with occasional oil contamination, it was finally leaking.
Swapping in new seals was a fairly easy task, and we completed the job in several hours. It required pulling the axleshafts from the housing and unbolting the differential bearing caps to pull the Air Locker from the differential housing. No special tools or gearing setup was required, and everything was reassembled back into the housing in the same configuration it had been in.
Time was on our side so we pulled the differential cover to release the gear oil, then let it sit about two days and drip most all of the lube off the locker before we started the work. It didn't make the shop odor much better, but at least the parts weren't as slimy to work with.
Note that there have been some variations in copper line size and O-ring type over the years, so you will want to confirm the exact parts you have in order to get the correct replacements. ARB, at some point, also swapped from round-profile O-rings to four-sided O-rings. Should you need to get O-rings from a source other than ARB, know that ARB recommends ones made from Viton with a durometer rating of 75. They are rated for operation over a working temperature range of about -15 to 400 degrees F, but can withstand higher temperatures for short periods of time.
As mentioned, ARB seal failures are fairly rare. Nevertheless, know that if you have an issue, seal replacement is not terribly difficult and you can make your air locker last the life of your vehicle.
We disconnected the air lines and straightened the copper tubing. After checking that our differential bearing caps were marked as to their left- and right-side locations, we removed the bearing cap bolts and caps.
Using a pair of pry bars, we worked the locker out of the differential housing. Whether the ring gear backlash is set using threaded adjusters or shims, you will want to keep track of their exact positions for reassembly. Our Dana 60 uses a shim pack to set the backlash.
With the seal side of the locker clear of the differential housing, we were able to pull the shim pack and the ARB seal housing off of the locker.
With the seal housing removed, here's a look at our old seals. You can clearly see that the outer seal is twisted in one area. This almost certainly occurred during gear setup when the axle was originally assembled. We were careful not to repeat this sloppy mistake after installing our new seals.
You can purchase replacement seals, and a new seal housing, if needed. The seal housing itself is all metal construction and should not wear over time.
Here's a look at the two types of Viton O-rings in use on ARB air lockers. Ours had been originally installed with the four-sided variety, but was designed for the round style, which we used for replacement.
With new O-rings lubed and slipped into their locker grooves, we assembled the shim pack and gently pressed a new seal housing over the seals and onto the locker. Then the locker was pushed back into the differential housing. Before fully seating the differential in the housing, it's a good idea to align the copper tube as close as possible to its final position.
The copper line on the seal housing may be routed in several ways, depending on the particular axle you're dealing with. On our axle, the copper line was routed through a hole in one of the bearing caps. After checking the alignment of the copper line, the caps were mounted back in placed and their bolts torqued to spec.
We bent the copper line to route it clear of the locker body and out the threaded fitting in the differential housing. You want to ensure that there are no rub areas or strain on the copper line that could cause leakage issues in the future.
When we had removed the outside air line and internal copper line from the housing, we found some significant hose wear above the compression nut where the support spring sat. We cut a portion of the plastic tubing off to give us a fresh end to work with.
Our axle used the original-style fittings (lower). We replaced them with newer ARB 5mm fittings (upper), which require fewer pieces. ARB also now offers a heavier 6mm tubing with a new fitting system that allows the air line to exit horizontally or vertically at the axle.
Our last step before closing up the axle was to connect the air line and do a quick check to ensure that everything was installed correctly and there were no air leaks.