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  1. #1
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    ARB air locker not engaging

    Well, finished hooking up the compressor and ARB air lockers. Tested the front locker, works just fine. Tried testing the rear locker but it won't engage at all. It's not the solenoid or the air line. Hooked my shop compressor up directly to the rear locker and set it to 150psi, still no luck. It's been a year and a half since it was installed, but I have also driven it regularly since then.

    I'm hoping to not have to crack it open if I can help it, but it is looking that way. Not sure if moisture worked its way into the locker and is frozen (it's been highs of about 20 and lows in the single digits lately) or if something else is wrong. I put a hot air gun on the pumpkin for about a half hour to try to defrost it, not sure if that was enough though. It's not leaking either as it does pressurize and I don't hear air coming out of the breather. So either the line inside the pumpkin is blocked or the piston is frozen in place due to either water, grit, or rust.

    I'm going to take it out for a drive tomorrow or Saturday to see if I can heat the diff up enough to be sure it's not due to frozen water. If that doesn't work then I'm probably going to have to pull the diff apart to see what is wrong with it.

    Any thoughts?
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

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  2. #2
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    Took it for a drive today to warm up the diff to see if that would help. No dice.

    Drained the diff and took the cover off to see what was going on. The locking sleeve is not moving at all when air is applied. Ended up undoing the bulkhead fitting to get the copper line out to check for kinks and didn't find any, but what I did find was the jam nut that is used to compress the seals in the bulkhead fitting to seal off the copper line was rusted and covered in gunk. Turns out the little piece of hose the guy that did my diff used to seal it until I could get the air lines hooked up was cut at an angle and apparently it was too much of an angle to allow the hose to seal properly inside the push connect fitting and it let water and junk in.

    So now either the copper line is plugged with gunk and that is why the locking collar won't move, or water got all the way inside and caused damage that is preventing the sleeve from moving.

    Based on how it is constructed when looking at the parts diagram for this particular model, I'm really hoping that it's just that the copper line is plugged with crap. The way he routed it left a U shape in it that theoretically would have trapped all the water and crud. It goes from the top of the diff housing down past the bottom bolt for the bearing cap and then back up to the top of the housing and into the seal housing that fits around the diff shaft.

    Tomorrow I might try hooking the line back up again and checking for leaks using the compressor in the engine bay. I couldn't tell with the shop compressor since the setup I am using to hook to the diff has leaks of its own that I wouldn't be able to hear any small leaks in the diff over. My thought process is if I don't hear any leaks at all inside the diff then the most likely culprit is the copper line is plugged with crap. If water had made it all the way to the seal housing then it would have rusted inside there as well and caused the o-ring seals to start to fail and air would leak past them. I would be so lucky that all this fix will need is me to cut the copper line close to the seal housing, clean out the rest of the tube, and then solder it back together. I am really, really not wanting to have to pull the diff out and crack it apart to get this fixed, and potentially end up with a ruined diff due to rust. The parts I would likely need to repair it would run me over $400 if the diff flange is rusted, plus the time spent doing all this.

    While I get that I wouldn't have this problem if I had just hooked the lockers up right off the bat, it's pretty frustrating that this is all due to someone not bothering to cut a piece of hose square.
    2008 H3 Alpha

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  3. #3
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    Sounds plugged. Not sure I buy the frozen moisture theory...more likely something physical blocking the tube. Maybe try probing the tube with some some weed-eater line? Or possibly a squirt of PB? My thinking is these would be last ditch moves before replacing it.

    I would caution against hooking it up to shop air, as you can blow the seals out of it if the pressure is too great.

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    JPaul (12-27-2020)

  5. #4
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    I'm going to try one last ditch effort before pulling the diff out. I am going to take the cover back off today and cut the line closer to the seal housing and check the cut off line for blockage. If I find it to be plugged I'll temporarily hook the bulkhead fitting to the shortened line and see if it works then. If it engages then I know it's just a plugged line. I have some 3/16" copper-nickel line I can use as a sleeve to splice the tubing back together (soldering it in place) if I can get the blockage cleared out.

    When I first tried shop air i had it regulated to 90psi but kept increasing it to 150psi as I was trying to get it to engage in case it just needed some coaxing. But after seeing the locking sleeve not move at all while doing that I realized the sleeve is either completely frozen in place or something is plugged.

    I really hope it's just the line being plugged and doing the above will fix my issue.
    2008 H3 Alpha

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  6. #5
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    Well I am stumped. I cut the copper line and found there was diff oil in it. Blew the cut off portion out with carb cleaner and it is fine. Hooked the bulkhead fitting up to the line going to the locker and still cannot get it to engage. That side is full of oil as well. No air leaks, no fluid coming out under air pressure either. Locking sleeve still doesn't move. The oil in the line was clear so it's not contaminated as far as I can tell

    Tried applying vacuum to the locker instead with a hand vacuum pump and it would hold vacuum surprisingly well. I was hoping to get the fluid to come out from inside the locker by applying vacuum but it's not doing anything.

    I may just have to break down and take the diff out to see what the heck is going on.
    2008 H3 Alpha

    "Live free or die: Death is not the worst of evils." - General John Stark

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  7. #6
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    Sprayed it out with carb cleaner and then a bunch of PB Blaster. Heated it up pretty well with the hot air gun. Still nothing. Ran a wire inside the line going to the seal housing, no blockage there for sure. As far as I can tell the locking sleeve is seized. No air leaks whatsoever.

    I had to button it back up again for the night. Maybe sitting overnight with PB Blaster will free it up, but I'm not counting on it. Looks like tomorrow I'll be pulling the carrier out and cracking the locker apart to see what is going on.

    Getting the carrier out isn't too concerning to me, but getting it back in is new to me. Will I need to get new shims or can I reuse the old ones? I am assuming I just need to make sure it's shimmed the same amount on each side as before since I'm not changing the gears. I don't have a case spreader though, so I'm wondering how big of an issue that will be when trying to get the carrier back in. I looked over a write up specifically on the 10 bolt and they said a spreader is optional.
    2008 H3 Alpha

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  8. #7
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    ARB air locker not engaging

    The 10b is pretty user friendly...I never use a case spreader on them. The 10b does use external shims on the carrier and they will fall out (along with the races) as soon as you pull the carrier. Just be aware and get ready to catch them. Keep them in the same position when you reinstall it.

    I have not done an ARB install on a 10b but I have done numerous D44s. The two diffs are very similar, and the D44 version of the ARB uses its own special shims at the seal housing (in addition to the carrier shims). So perhaps the seal housing is not properly shimmed? That would certainly cause it not to work.

    Post some pics when you get it apart.
    Last edited by 4speedfunk; 12-27-2020 at 10:17 PM.

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  10. #8
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    On the D44s, that ring has two seals on the ID of it. They are about 1/8” apart, and the air pressure is contained between them. Then on the snout of the carrier, there is a tiny hole that is supposed to reside between these two seals. Air pressure gets channeled thru this hole to the “mystery guts” inside the diff.

    If the ring is not installed properly the hole could be covered up by (or located outside) the seals. It’s a pretty small mechanism considering the end result. That’s the first thing I would check...make sure the path of air pressure leads to that tiny hole.

    Additionally you might be able to bench test the locker by using an air needle (like for a football) inserted into that tiny hole. If you can get it to work like this without the seal ring...then it would definitely point to a problem with the ring installation itself.

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    JPaul (12-27-2020)

  12. #9
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    Awesome, thanks for the insight 4speed. I'm going to take it out tomorrow and see what I can find. Hopefully it's something minor (because having to take the diff out isn't minor...) and I can get it working and back in. I have new tires on the way and was hoping to have the lockers all hooked up so that once the new tires were on I could take it out for a spin.
    2008 H3 Alpha

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  13. #10
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    4speed, I realized I might need to take the bearing off the carrier to get the seal housing off if it turns out it was installed incorrectly. I see there is a special multihundred dollar clamshell tool I can get that doesn't damage the bearing, but I'd rather not spend money on something like that when I'll likely use it just this one time. Would a standard bearing splitter work ok? I have a 20 ton press to get the bearing back on afterward, and can rig up something to use the press to press the bearing off with the splitter.
    2008 H3 Alpha

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  14. #11
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    Hey.

    So...

    Everything I have read talked about needing prybars to get the carrier out.

    Swhile it is only 16 degrees Fahrenheit out...

    Should the carrier really just fall out once I loosen the bearing caps???

    2008 H3 Alpha

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  15. #12
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    Well, it's not the locking sleeve that is seized. Cracked the whole locker apart and the sleeve came right out. So that's good. Either the seal/piston is completely stuck (seems highly unlikely) or the airway is clogged or the seal housing is misaligned.

    The guy that did the diff for me says he bench tested it, but I am starting to really question that now.

    Unfortunately I have to get the bearing off to get the seal housing off and I might end up trashing the bearing. I think I have to use a bearing splitter because there is no way to get the fancy collar type puller on the inner race.

    Joy.
    2008 H3 Alpha

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  16. #13
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    Well. Got the bearing off (without destroying it I might add).

    Put some air to the hole in the flange and the sral/piston popped right out, so that was fine.

    Sure enough when I then looked at the seal housing it looked like the hole was full of crud. Blew it out and lota of little bits of crud came out.

    All this BS because the guy that did the diff for me cut the piece of hose he put in as a plug at an angle which prevented it from sealing fully.

    Granted, if I had just installed the compressor and the air lines soon after getting the diff back it wouldn't have been a problem. However, that doesn't excuse him from being lazy with plugging the line. This is precisely why I am so reluctant to have anyone else do work for me. More often than not it ends up being shoddy in one way or another. And I'm still very concerned that the carrier fell out of the housing once the caps were removed. Hopefully it's just the cold that caused it. But it still seems like it should have been at least a little bit snug still.

    Now to clean everything up and get it put back together again.
    2008 H3 Alpha

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  17. #14
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    Given the loose fit, you should correct the carrier bearing preload while you got it apart. Some 10b shims would be needed...prolly in the .002” to .005” range. Most likely there are stacks of shims in there already, and you should try adding a .002” or so, until the carrier fits snugly into the case.

    Of course this adjustment will change the backlash. In fact, if the carrier fell out like you describe...the backlash could not have been measured accurately anyway. You can’t measure backlash if the entire thing is shifting right-to-left inside the case. So get the carrier bearing preload fixed first, then correct the gear set backlash.

    I won’t go into all the adjustments on here or it will turn into a novel. But the goal is to have the carrier fit snug (gently tapped into the case with a hammer) AND have .006” to .010” of backlash.

    Don’t forget the ARB seal housing also has shims that need to be thrown into the mix. Check the ARB install instructions for that.

    Stay calm. It’s not difficult. But it can be tedious. Dial indicator with mag base, and dial calipers will be needed.

  18. #15
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    I got everything cleaned up and put the carrier back together enough to be able to test the locking mechanism.

    It locks now, but it also has an air leak in the piston seal, and I buggered one of the o-rings for the seal housing. I am guessing there must have been an installation cone for the seal housing as the flange it fits onto has a sharp edge (which is how I wrecked the o-ring) but I don't have it. I'm hoping the piston seal leak is just due to the cold, but I might have nicked it as well when putting it back in. I'm letting the carrier warm up a bit in the house before testing it again to see if that helps.


    That is discouraging about the preload apparently not being set correctly. Unfortunately I can't find the instructions that should have come with the locker, both in my personal effects and online. All I can find is the parts diagram.

    I didn't see any seal housing shims, either installed or in the parts diagram, and it doesn't appear that there would be any. The seal housing rides precisely between the flange and the inner bearing race, and the shaft the race presses onto is filleted to match the race. The wear marks from the o-rings are right where they should be.

    Either way, now that the o-ring for the seal housing is buggered I am dead in the water until I get some replacements, may just have to get the whole seal housing since I cut the line to it. This is not how I was hoping to be spending my time off...
    2008 H3 Alpha

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