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Anyone had this problem with an ARB Airlocker?

valveamp

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Joined
May 30, 2011
Messages
287
Hello everyone. I installed an ARB Airlocker in my rear differential, along with the small compressor from ARB. Been installed, for about a year with no problems, but I've only engaged it about 2 times. The problem occurred after a fairly long drive home on the freeway this past weekend, about 1 1/2 hours each way. I saw a wet oil spot on the driveway under the driver's side fender. I traced it down to coming from the ARB compressor that's mounted on top of the driver's fender under the hood. At first I thought the compressor must contain oil, but I read that they do not have oil in them. What I read on line is that the problem is gear oil coming out of the differential up the compressor air line and then out of the compressor (somewhere). There seems to be differences of opinion as to what the cause is. Some people say it's the O-ring seals inside the differential. Others say it's a clogged vent. Some people just live with it. Anyway, I've never read any discussion, here, regarding people having a problem like this with their compressor. A couple things I intend to do. One is to verify the vent on the differential housing is not clogged. The other is to verify that the locker still engages properly. If anyone has had this issue and solved it, I sure would like to hear from you. Oh, I forgot to mention I don't seem to have the problem on short drives around town. Thanks.
 

Boss Hugg

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Jun 8, 2010
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I recently built a new rear end for mine. When I pulled the old one, it had pressure in it because the vent hose was stopped up with dirt.

For the new axle, I narrowed a full width housing to get the big bearings... I also welded on the U bolt Eliminators from Barnes 4wd. When I measured and located them, the drivers side bracket lined up on top of the vent hole. So I relocated it.

After driving it about 3 hours down the hwy, I found oil dripping from my rear end and spewed all around the end of the vent hose. Turns out, I had drilled and tapped the new vent hole to be located about 6 inches off the ring gear. So the gear was slinging the oil so hard that it was pressuring itself out the 5/16" hose. After topping off the diff a few times, I relocated the vent hose about 6" further out, and it's been fine since.

I'd say your problem is the vent is stopped up somewhere and the oil is getting in the air line somehow and pushing back up to the compressor. And I assume this because you've only engaged it twice in a year.
 

Boss Hugg

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And BTW, for someone's future searching and reference, the big bearing seals won't hold 60 PSI... I put regulated pressure on the vent line to try to blow the shavings out as I drilled and tapped the new hole I didn't think it would take that long, and I wanted enough pressure to make the shavings leave. Once they fell into the housing (with third member installed) they were going to turn around and come out. So the rubber in the left side seal blew out, reversing itself on the axle, and oil sprayed everywhere, including all over myself. I was able to reshape the seal after it blew out and get the spring back in place and have had no leaks there.
 

nvrstuk

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Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
8,604
If the vent isn't plugged...

The key to your post is "fairly long drive"... do you have new gears in it also?

IF SO, the issue is heat build up with the new gears not broken in yet...and/or it could be the very common problem of the 9" which just plain runs hotter than most rear ends.

Here's the fix...

Tim the head Tech at ARB in the NW years ago told me how to fix this as I had the same problem and he stated that it was a VERY common problem for Ford 9" owners.

You need to move the vent line off the tube on the 9" rear and drill/install a 3/8" minimum opening at or near the top of the diff housing on the opposite side of the ring gear. When doing this, tack weld in a small shield to deflect the oil that naturally is carried up the ring gear when you are moving.

I did this after the same symptoms you had after an all day crawl over the Rubicon and I have never had the issue in the 20 years since...

Sounds like a job, but it will fix it forever. You "might" get by with just going to a larger dia hose in the original location...worth a try anyway.

I've done this mod on all the Bronco rear housings since w/o any oil issue.

Good luck
 
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valveamp

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Joined
May 30, 2011
Messages
287
Nvrstuk, to answer your questions, yes, I installed new gears at the same time the air locker was installed. Went from the stock 3.50 to a 4.11. Interesting comment about moving the breather location. It just "feels" like it is a vent issue to me, although I don't have any evidence to back that up. Seems a little unreasonable that it's an o-ring problem when everything else works ok. Having said that, I'm no expert on how ARB air lockers work. Also, I agree that a long trip seems to be part of the issue. I have seen no evidence of an issue on short trips. Thanks for the tip. I'll see what I can do about your suggestion. I'm not really a welder (even though I have a brand new Miller in my shed!), so that adds a small complication, but not one that can't be overcome.
 

Boss Hugg

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It wouldn't take but a few minutes to pull the vent hose barb out and check it. It may have a screen built into it. Spray brake cleaner thru it to see if it lets it thru. Then put some air pressure to the hose to make sure its clear.

I suspect it's stopped up somewhere, building pressure in the housing and pushing it out the air line system. That line comes all the way to the carrier, basically, which should always have oil on it after a couple miles. This oil gets pressured thru the seals which probably only seal one direction (or it's building a LOT of pressure) and out thru the air line.

Check the vent. Easy fix.
 

nvrstuk

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Just a Bronco driver for over 50 yrs!
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It's amazing how much heat new gears develop. Last month at Moab w/brand new 5.13's

In 20 min of 65mph at Moab with less than a 100 miles on them, I would use my infrared gun on the 9" housing and check temps below the oil level--it would read 155deg F.

We'd sit and let it cool till 100F and then we'd take off... did this each day till we got back.

Haven't had a chance to check it since we're back home, but I will and the temps always come down- always do...
 
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valveamp

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May 30, 2011
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287
yes, I need to check the vent for an obstruction. Don't have time right now, but next week I should be ok. Really feels like the vent should be clogged to cause this problem. Anyway, doing a little shopping, I came across this (link below) on the Bronco Graveyard website. It seems to be specifically for the problem I'm having. I can't find any information on how this "device" is installed. Were does it go? Anyone use one of these?

http://shop.broncograveyard.com/ARB-Diverter-Dump-Valve/productinfo/21949/

Love to hear from someone who has used this part and where/how they installed it.
 

nvrstuk

Contributor
Just a Bronco driver for over 50 yrs!
Joined
Jul 31, 2001
Messages
8,604
If the line was clogged the pressure build up in the housing would force the oil somewhere else...out the axle seals probably...


This "dump valve" looks like it's designed to make sure your compressor doesn't get any oil in it when the oil is pushed up your vent line all the way to the compressor!!

Band-aid for the problem is what this is...fix it right by fixing the vent so the pressure doesn't build up.

Course this is "best-guess", but it's the exact same issue I had 20 yrs back and identical to others that have fixed the vent issue by doing the same mods.

Good luck.
 
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valveamp

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May 30, 2011
Messages
287
Agree, need to verify the vent isn't clogged. Having said that, I still would like to know how this device works and where it gets installed. Sent an email to the Bronco Grave yard guys and, so far, no response.
 

bmc69

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Jun 11, 2004
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I've done the vent relocation mod nvrstuk described...stopped the oil from chronically coming out of the breather hose
 
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