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Don't ask me why it happens to some folks and not others....if I knew I would tell you. I am talking about the ARB air locker solenoid spitting an oily mist when you disengage the locker. I had my ARBs for about 18 months when my rear air solenoid started spitting a tiny bit of oil. It was hardly enough to notice....a film around the solenoid, that was about it. The other solenoid (for the front locker) was clean and dry.
What I couldn't figure out was why it would spit a little bit of oil when you disengaged the locker. As you know, the ARB lockers requires about 85 ~ 105 PSI of air for the locker to reliably engage. So you shove high pressure air down the blue air line when you turn on the lockers. Some period of time later, you disengage the locker and out spits some oil. Does that make sense? How does the oil get in the air line? And why doesn't the oil blow out somewhere when you push 100 PSI at it?
I spoke with a friend and I think we came up with a possible explanation. When the o-rings begin to fail (leak), they allow oil to seep into the void between the two o-rings. This happens as you are driving, even in 2WD going down the highway. When you then pressurize the locker, the o-rings flex a little bit and seal (as they are suppose to seal) but the oil doesn't go anywhere. (I don't have a leak down problem and can go well over 30 minutes with the locker engaged without the compressor ever cycling). Then, when the locker is disengaged, the air rushes out and with it goes some of that oil up the air line. Eventually, it makes it all the way out to the solenoid and you notice it. In the mean time, a small amount of oil leaks back into the area between the o-rings and entire cycle repeats itself. We may be completely wrong....but until you come up with a better explanation, this is the one I am going with.
I lived with the spitting oily mist for another couple of years until it finally got annoying enough to do something about. In the mean time, the other air solenoid is still clean and oil free. I believe the reason is for one of two reasons....perhaps, my Warn hub kit which keeps the front axle from turning except when I am out wheelin' may have something to do with prolonging the life of the o-rings in the front axle).....OR.....I just had a slightly defective o-ring in the rear locker from day one and it finally started leaking. Doesn't really matter why I guess....it needed to be fixed and that is what this write-up is about.
If you read my ARB installation write-up, you will notice that replacing the o-ring is really a portion of the complete ARB installation. To replace the o-rings, the ARB differential needs to be removed, the o-rings replaced, and then the locker installed again. So...now that you know what is going to happen, let's get on with the details. Note that I have a D44 rear axle with disc brakes. The first couple of photos/steps may not match your axle and brake arrangement.
With the tires removed, the disc caliper mounting bolts are removed and the caliper is separated from the mounting bracket. There is no reason to remove the brake hose from the caliper itself. I used some bailing wire to hold the caliper up and out of the way.
Next, the D44 axle shaft must be removed from the axle tube. This is necessary since the splined end of the shaft engages the ARB locker and it would be impossible to remove the locker with the axle shafts still installed. The D44 has 4 nuts that hold the axle retainer in place. As seen in the above photo, a socket on an extension is used to access the nuts (through the hole in the flange). Remove the 4 nuts and set them aside as they will be reused during reassembly.
Sometimes the clearance between the axle retainer and the bolts it mounts on can be tight. I used a small punch to gently move the bolts back and out of the retainer plate. A couple of them were tight and it would have made for a more difficult job. With the bolts out of the way, pull the shaft out of the end of the axle tube. Since I had used some RTV to help seal the oil seal when I last put the axle shafts in, I had to give a gentle tug to break the RTV bond. You will probably get a little oil running out of the tube, this is normal. Have a couple of paper towels handy and use them to plug the end of the tube. Repeat the above steps for the other axle shaft.
At this point, I removed the bolts holding on the diff guard and the diff cover. My D44 has an axle truss on it. The truss is used to provide a mounting point for the triangulated rear upper control arms. A support bracket is attached to the truss and the top 3 bolts diff cover bolts on the housing. The bracket was removed to allow easy access to the diff cover.
With one of the top bolts still slightly holding the cover in place, I used a dead blow hammer to dislodge the cover enough for it to drain into the oil catch container. Did I mention that I cheated this time and put the TJ up on a lift? Standing up to do this is a lot easier than laying under the vehicle (so I found out!) Many thanks to Troy (Toys by Troy) for the use of the lift.
With the cover off, the ARB differential can be seen. Note
the copper air line that brings the air in through the bulk head fitting and
into the seal housing. In the pic above, the bearing cap is covering the