Differential / ARB Issues, Need Advice **BINGO**

[Tedster100]

Last week I had the Bronco out and about a mile from the house it made a little bang in the rear end that sounded like the t-case popping out of gear. After that - no forward movement. I stopped and looked to see if I had a u-joint or drive shaft problem but everything was good. After getting back in and putting it in gear and releasing the clutch it just sat there. The trans was in gear and the drive shaft spinning, just no forward movement. I know because I left it idle in gear and got out to look, shaft spins but nothing to the wheels.

Back up 2 years..... I purchased front and rear built axles both with ARB lockers from a member who had them built at a local shop. I put them on last summer but never got around to the compressor, air lines and wiring for the ARB until about a month ago. With the pressure set to specs, I tried to operate both lockers in the garage with the Bronco on jack stands just so I could verify they worked properly. The front was good but the back just blew air into the axle and blew gear oil past the axle seals. Obviously there is a problem with the ARB and the axle vent. When I put the front axle in I noticed that the ball joints were old and a couple shot (the off road shop supposedly changed all of them but that's not what I found), this made me worry about the workmanship on the locker, diff, etc... I ran the rear end without the ARB operating for a few short trips, maybe 30 miles total and this is what happened.

I've pulled the rear diff and everything appears ok. Gears look fine, there's no visible issues with the diff. Putting my fingers inside I can feel the splines for the axles and the spiders are turning so I'm not sure if there is something internally wrong with the ARB or what. Is it possible that the ARB blew it's seal and engaged the locker beyond the normal operating range to the point where it seems like I have no ring gear to engage? I'm going to make up a bench mount tomorrow & then start checking into it more. Does anyone have any idea what could be wrong?

 

[broncnaz]

So no metal in the oil right? I would suspect that maybe the pinion has busted. Hold the ring gear and try to turn the pinion.
I guess another issue could be the ARB clutch gear has failed although I would think you would still have some power to the ground even if it did fail. So Im thinking something is wrong with your pinion or maybe even the splines on the yoke or pinion.

 

[nvrstuk]

X2 what Bronconaz said...not much to "lock up" inside...

http://www.arb.com.au/media/products/air-lockers/2-RD119.pdf

 

[Tedster100]

Yea, no metal in the oil. Pinion turns the ring gear now that it's out, maybe it's just doing it by friction? Guess I'll have to tear into it more. Odd thing about it was that there was only one small pop then nothing, the drive shaft spun and just a little bit of force was being applied to the axles but not enough to move the Bronco. There was no grinding that you would expect if the splines on the shaft or yoke were damaged allowing it to slip.

 

[welndmn]

It's really odd for an ARB to fail where you have no drive, it's really common for 9" rear ends to crack the pinion support bearing thus tossing off the ring gear engagement and giving you no drive.

 

[broncojo]

I'm sure you looked but do both axles look good, as far as splines and ends.

 

[bmc69]

It's really odd for an ARB to fail where you have no drive, .

That was what I was thinking too...although I've never had one of my ARBs fail in any fashion. If the locking part fails, all that means is that you are left with a standard open differential.

 

[Apogee]

I'm sure you looked but do both axles look good, as far as splines and ends.

I was wondering the same thing...axles too short, barely engaging the splines on the ARB? Strip one out and it won't go anywhere unless you were to lock it, which you can't do because you need new o-rings. I'd start addressing some of the issues you can be pretty certain exist, like getting the locker to function properly, then trying to figure out what else is wrong. Troubleshooting problems that are stacked up more than one deep can be a challenge.

 

[Tedster100]

The axles are like new, no signs of any wear or marks on the splines where they may have come out of the carrier. So tonight I fab'ed up a quick bench mount and got it up where I could get a better look. The pinion looks good and solid and turning the pinion rotates the ring gear as it should. A couple things were obvious as soon as I got it up on the bench mount, first the air fitting on the locker is loose. Not sure if it's a rotating type of fitting, I'm saving that part for later. The other issue is that all the ring gear retaining bolts were loose and appear to be too short (see the pictures). It looks like I've got a little over .28" of thread engagement from the bolts into the ring gear. There does not appear to be any damage to the carrier and none of the bolts were actually out but some were backed off at least 3 turns so it was a matter of time before something bad happened.

So, I'm still not sure what's happening. My goal is to get some longer bolts and torque them to specs after installing them with loctite. Once that is done I'll start checking the air locker out. I can put it on bench regulated air and operate it to see whats going on. I wonder if the locker can go into an open condition if the seals are blown or something wasn't installed correctly? This diff probably has 2500 miles on it and never had an issue until I hooked up the air locker so my thought is that it might be the problem. The locker was never really used, I put air to it in the shop once everything was hooked up and it blew air into the axle, that was the only time it was engaged, never under a load yet.

I also thought the wear pattern looked all right but after looking at the picture it appears maybe a little more coarse than I thought it looked in person, any thoughts?

 

[broncosbybart]

Good luck finding ring gear bolts for it. ARB doesn't carry them anymore. That is a discontinued locker. The newer model uses regular hex bolts. I suppose you can try and use some generic grade 8 Allen's.

The air fitting is supposed to pivot a bit.

The locker is very easy to take apart. Do this before you put new bolts in the ring gear. You will need to remove the ARB from the 3rd member to take it apart. It is a very simple device that uses air to push a locking collar against one of the spider gears. Several small springs push the collar back when air is released. My guess is that either the plastic air line is broken or that the o-rings in the seal housing are no good. Poly Perf or CCOR should be able to get you small parts for it.

I doubt the ARB is broken to the point of causing no movement. There would be major damage to the spider gears or housing. It is an open carrier in essence. The locking part has no relation in its integrity. That said, I have no idea on what is causing your issues without seeing it. Let us know what you find.

My guess would be broken/missing center pin in the diff or one of the axles are too short. Probably the latter. Especially if you can't see any wear marks on the splines.

 

[bmc69]

I wonder if the locker can go into an open condition if the seals are blown or something wasn't installed correctly?

But ..what do you mean by "open condition"? I keep going back to the fact that it should simply be a stock-behaving open differential if the locking part is not engaged, is not even hooked up, or has failed for some reason.



right??

 

[bmc69]

I doubt the ARB is broken to the point of causing no movement. There would be major damage to the spider gears or housing. It is an open carrier in essence. The locking part has no relation in its integrity. .

Exactly!

 

[Tedster100]

But ..what do you mean by "open condition"? I keep going back to the fact that it should simply be a stock-behaving open differential if the locking part is not engaged, is not even hooked up, or has failed for some reason.



right??

Yea, this has me befuddled! It made a pop like the t-case jumping out of gear and stopped moving. I actually stood next to the Bronco with it in 1st gear idling and the drive shaft was turning the pinion but there was only a slight forward lurch. At the time I really thought that the bolts had come out of the R&P or had sheared and the lurch was just from the friction of the ring gear rotating on the carrier. I guess I'm going to have to bite the bullet an tear her completely down to see what's up. Never set up a R&P before but I can read, have the tools and there's a first time for everything.

 

[Viperwolf1]

Are you sure it wasn't the splines in the driveshaft slip joint that were slipping?

That ARB looks very odd. The air seal is on the opposite side as mine.

 

[welndmn]

Take a bunch of pics for us, the 3 rd memeber, the pinion support inside and out, the splines on the axels....

9 inches use two sizes of ring gear bolts, most kits have bolt sizes so that could of been an easy mistake.

 

[bmc69]

Yea, this has me befuddled! It made a pop like the t-case jumping out of gear and stopped moving. I actually stood next to the Bronco with it in 1st gear idling and the drive shaft was turning the pinion but there was only a slight forward lurch. At the time I really thought that the bolts had come out of the R&P or had sheared and the lurch was just from the friction of the ring gear rotating on the carrier. I guess I'm going to have to bite the bullet an tear her completely down to see what's up. Never set up a R&P before but I can read, have the tools and there's a first time for everything. The farther I go down this road the more I see that the shop that built these axles for the PO totally F-k'd him (and me) BAD.

If it was properly set up before and you do not remove the pinion now, setting the ring back up properly is stupid simple. I measure the backlash and do a pattern check prior to disassembly/removal of the carrier. Put both back where they were when you re-install it.

Very, very curious to see what is going on. I've hammered the crap out of ARBs for many years and they are one of the few pieces of axle hardware I've never managed to ever break.

 

[broncojo]

That ARB is different than mine also, not sure why. Did they change them over the years?

 

[broncokak]

That ARB is different than mine also, not sure why. Did they change them over the years?

Yes, it looks like mine but I know the newer ones look different.

Have you confirmed it is not a broken pinion shaft yet?

 

[Tedster100]

Ok, let's re-cap.

Bronco make a little pop like the t-case coming out of gear and then no power to the wheels.
Put it in drive and the driveshaft / pinion spin perfectly but still Bronco no go
Pull the third member, all the splines, internals, pinion & ring gear look A-OK
No evidence of any violence or metal shavings what-so-ever in the carrier, case or axle.

Soooooo... I check the lash & gear pattern and pull the bearing caps, again, everything is as it should be. Bearings look clean and like new. I throw the carrier up on the bench and check out the pinion. Again, bearings, shaft and gears are in-tact and looking like new. Thought about pulling the pinion to check the shaft and then decided against it. Figured I'd investigate the carrier a little more first. Took the bolts out of the ring gear and went to work it off the carrier and this is what I found.

I've never seen a complete and total failure like this without it spitting out a bunch of pieces of steel. The carrier sheared or broke right at the ring gear and the ring gear acted like a flange to hold the two pieces together. Frickin' Bizzare!! This really blows, I've never even run the locker while it was locked. I did jump on it once hard enough to crack a u-joint but I can't see that causing this kind of failure. Guess I'm gonna have to get a new one.

 

[tasker]

it was the blindfold course that did it! Sorry Ted!