ARB still broken but found the problem

SO after many months of my rear ARB not functioning I finally have a fix. I had a couple of problems going on. first of all the seal housing of the RD99 was too far out on the flange cap assembly so the seal would slip off the end and leak air. that has been fixed but the locker would still not function. So I tore it apart this weekend and compared the locker to the pictures and found some internal damage. The "clutch gear" and the "side gear" are supposed to mesh and allow full engagement of the locker. However the edges have "broached" or in other works ground down the edges to a 45 degree angle. that allowed the locker to engage during the bench test but not under any load since the edges were worn to a 45 degree angle instead of a straight edge. So I basically stripped the side gear and clutch gear. Parts have been ordered and I am taking pictures so I'll post them when I am done.

The edges should be straight, not angled 45 degrees. TIme for a new clutch gear.

Here is a post by truehi9 from pirate explaining the issues with the ARB.

As stated by StinkBug this isn't a Hi9 issue. These issues were brought to my attention by Twisted Customs before we ever built the first Hi9.

Issue #1 air ring popping off the end of the journal
Issue #2 broaching/corners rounding off of the clutch gear

I've talked to every salesperson, tech person, the head designer of the RD99, and the president of Air Locker USA to help resolve these issues. I've sent emails with blueprint changes that would help and would cost nothing but a different number being put in the machine. The 1st answer I always received was "HMMMMMMM that's the first we've ever heard of that, then the answer turned to "must be an installation issue".

After 3 1/2 years, and only with the EXTREME help/voice of Tim Lund (former ARB head tech guy) I was able to have a few things changed to eliminate the first issue and help the second.

Issue #1 The air ring sits flush with the journal end, there is a taper that helps the orings seat but the taper leaves zero tolerance for movement and the airring would occasionally pop off the journal at an angle.

The fix, leave the journal longer to allow a safety margin if there is movement, cost nothing, just machine less off the end of the journal.

Issue #2 pictured in the post, the clutch only engages the side gear by .060 of an inch.

An easy way to help longevity not cure this is to machine the step that the gear seats against to allow more engagement, cost nothing just machine a little more off the step. Its only .020 more but that gives 25% more engagement. This change in most, not all cases (depending on usage) has increased the lifespan of the clutch gear.


As of the middle of October 2008 the ARBs I've received have both of these changes made. The way to tell from the outside is that they have also went to laser etching the numbers from hand numbering the ARBs and the laser etched ones are from the latest run with these changes.


It appears Dustin Webster has also had some good results with an extreme pressure 250 wt. gear lube.

Spidertrax has recently come out with a clutch gear made with different material that should be an improvement.

Running more pressure can also be done (holding the clutch gear in place better) with the increased safety margin of the airring placement.

So the combination of these items should greatly improve the reliability of the 9" ARB. It will never withstand engaging the locker with one tire spinning but strides are being made by a combination of people to improve the existing product.

just got my ARB parts in so I can fix it tomorrow, finally.

Sweeet!! That's great news - i'm glad there is finally a solution!

he showed us up so much without the locker. think of what he will do with it.

nah, it was all strategie. send someone else first to show me the line.

What happened on 16?

I remember you going first very very clearly! Maybe that's the wet day strategy to get on the rocks before the mud is slopped around...

or maybe we're just dumb

i have had a similar problem with the RD109 35 spline dana 44 units, i know i didn't engage with the tires spinning , but that was the explination i got from arb for the failure of the clutch gear.

Having torn it apart and discovered the internal workings I can see how inadequate air pressure can cause poor engagement of the clutch gear with the side gear. If it happens once it will start the "broaching" and round the edges of the gear off. If the arb is actuated with the wheels spinning it could cause the "broaching" and if you engage the locker and hit the gas hard it may not be engaged and cause the " broaching". Once the arb is actuated it still needs to move slightly to allow the clutch gear teeth to line up with the side gear teeth. So when actuating the ARB you should be at a complete stop and then actuate and then inch forward a little to give the teeth a chance to mesh before stepping on the gas. There is very little overlap of the clutch gear and side gear as well. I'm suprised it lasts as long as it does. I'd estimate only about 3/16" overlap of the gears. the wore out edges depth plus about 1/16". I did some modifications to the housing while I was in there so either it will work better and engage farther together or it will totallly just crumble into a ball of steel wool. I'm also switching to a higher rating pressure switch 90-120 instead of the stock 85-105 and getting a larger air resevoir. May be overkill but I got time.

Locked_N_Loaded wrote:

What happened on 16?

I remember you going first very very clearly! Maybe that's the wet day strategy to get on the rocks before the mud is slopped around...

or maybe we're just dumb

It was one of those spots where I picked the right line at the right time and used second gear and it worked. you will have days like that. And I did go up before it got all sloppy.
I did assemble the ARB with the new parts and modifications. ALso assembled the 3rd member and did the best I could with torquing the ring gear bolts down. (anyone have any tips on how to torque the ring gear bolts down with the 3rd member on the table?) Tomorrow I'll replace the studs in the 9" housing and put it all back together. the lowest stud does not have room to come out since the shaved portion of the housing is in the way so I may drill it out and tap threads and put a bolt in there. It could second as a drain for the housing for when I have to fix the arb again.

Rear is assembled and all locker tests passed! Jeep is finally back on all 4 wheels again.