Outer Limits 4x4 Board

As the title - it is the latest diff lock for the large Pajero diff.

I have one and since new it does not hold pressure when under load and the compressor stays running. When no load is on the diff it locks nicely.

I took the diff out and returned it to the fitter who tried again and it is still leaking.

The installer is an ARB agent and has done hundreds of air lockers without fail. He is a competition 4WDer and knows how to set them up. But this one has him puzzled and after a few phone calls to other installers they don't know what might be up.

Any ideas? And does anyone else have this new locker? When I release the locker the air released is a very small whoosh compared to the front RD110.

It is beginning to be a piss off as it is a bit of a job taking the diff out cos it ain't a puny Hilux diff that you just lift into place!!!

Hi NJ,

So you gave up the idea of a Mistsu rear locker?

starting with the obvious,
leaks in the air line
leaks at the compressor

not so obvious

faulty compressor or in adequate compressor.
perhaps thre is a fault with the locker which your guy cant easily identify.

Bugger though it may have to go back to ARB for bench testing??

I am having trouble with the front locker in my NP, its sucking oil back up the air line & leaking all down the firewall. Doenst happen with my NL, so I am buggered what to do. I have tried to create a small air leak at the compressor, so that it doesnt hold pressure for days on end. The NL never held pressure for more that a day, so that might be the difference.

Good luck with the rear & yes it is a heavy 'mother' not something you would want to drop on your chest!!!

Hi Ian,

Cheers for your reply. I can't rule out leaks but when the diff is locked and there is no load on the axle assembly the diff stays locked without the compressor running.

But when attacking a hill or whenever load is applied the compressor starts. When i lift my foot it stops again. It is like something is flexing somewhere.

The compressor should be fine as my front one is hooked to the same compressor. I have not put a pressure gauge on it to see where it is cutting in and out but it is a standard old style ARB compressor.

I believe the oil coming back up the air line is pretty common and is also due to the O rings. I have had my front locker for 18 months now and ho problems. Love it, and the 154 was installed by the same person.

I got the 154 as I had some major vibrations and narrowed it down to something in the replacement locking diff I had got after I broke the one. And I wanted something I can lock instantly!!!

Glen

Hi:
Maybe check the solenoid on the top of your compressor to make sure its not around the wrong way, ie inlet and oulet around the wrong way. From memory marked 1 for inlet and 2 for outlet, check on your front one to make sure. i Recently put a second hand locker in my swb pajero and when i engaged it, the compressor would stop and start every 15 seconds or so. And the locker also wouldn't disengage instantly either. I Found that i had solenoid valve on top of compressor around wrong way, swapped it around and now works a treat. Don't know if this will fix it but hope this may help. Thanks mark

Glen, when you say "under load" do you mean significant driving load, or simply moving?

If you're driving along a flat smooth track (i.e. minimal load) with locker engaged, does the compressor run then?

I don't have any ideas either way, but it's not clear to me when the compressor runs.

Hi Mark, yes the solinoid is around the right way.

Scott, I mean significant driving load. if, for example I was in 2nd gear Low ratio, locked diff on flat high traction surface at 1000rpm and opened the throttle compressor would run but when i button off, a few seconds later the compressor stops (after it has built up presure again)

If I am driving along said smooth track with it locked, all is well. It does take some load, bordering on wheel spin to make it do it.

Thing is - I can't even tell where the air is leaking to becasue as soon as there is no load on the diff or I stop it seals again!!!


Glen

OK - so, it's not simply turning which creates the leak, so it's probably not the o-rings or the surfaces they run on. But that's probably been ruled out by the bench testing anyway.

If it's a torque reaction thing (twisting of the axle under load) could you simulate that by trying to drive against the handbrake? Stick it on hoist / axle stands / jack & use a big lever to push/pull/twist things?

Does the problem happen in reverse?

Is there enough play in the supply line to the diff. It would seem that the twisting of the diff (under high load) may be pulling on the air line and may be allowing the fitting to leak. Is the air line routed near the motor or even run across the engine? The torgue of the engine may be pulling on the line or tapping a fitting on the compressor if it's close.

Glen, Can you get any dye into the compressor to show you just where the leak, you are encountering, is coming from ??? If you can, then that might show you just where to start from, ask this Fitter to try this for you, seeing he has it for bench checking. Best of luck mate, hope that you get it working as it should.

HI glen i have fitted a few of these and had the same problem with one and it ended up being a poor casting it was porous in the piston area so if you have it out again try putting petrol around it if you know what i mean

Hi Glen,

This is most likely the result of too little carrier bearing pre-load in the set-up of the diff.

The more torque you put on your axle the more outward force there is on your carrier bearings, and if the pre-load is too light then the diff can actually be forced out of position when the housing flexes apart.

The RD154 seal housing is held in place concentric to the carrier bearing so if you shift the diff at all then the diff will not be concentric to the seal housing, and therefore the seals get squashed on one side and loose on the other - and a leak can occur. If you find this to be the possible case then I would advise correcting the pre-load immediately as too little pre-load to this extent may also cause pre-mature bearing and ring and pinion wear and/or failure if not corrected.

Note: to test the current pre-load, mark the position of the adjuster nuts inside the bearing caps and then remove the locking tab from one of the adjuster nut and back the adjuster nut off 1/4 turn (90 degrees). If the adjuster nut becomes loose before you get to 1/4 turn then it was not pre-loaded sufficiently.

If the pre-load is found to have been correct then you will need to investigate your axle assembly for the possibility of being bent.

Hope that helps.

-daniel
AIR LOCKER

Hi Daniel, great to have you to write a reply

We did the carrier bearings up to proper spec the 1st time and this time they have been done up tighter. I can ask the ARB installer how much tighter he did them if it helps.

Glen

Hi NJ,

Did you get this sorted??

No, it needs to come out again. I just haven't got round to it.

It is a real disappointment as it is such a pain to take out.

It is wierd, sometimes it will leek with very little load, such as with it in on the street, just moving gently off the mark it will do it and other times it needs alot of pain, such as driving more agressively off road (but nothing like how some people use air lockers)

Funny thing is, I can put it in and preform a tight U turn on tarseal (painful I know!) and it doesn't leek

Worst thing is, it is just unuseable - well I can use it but I daren't as I know the consequnces of a not fully locked diff!!!

Thank goodness the front one is so good.... (but even then if I haven't used it for a while the compressor stays running until it has been uses a few times too!!!)

My installer has done hundreds of ARB's with no trouble. He made a comment the old air lockers with a 'bolt on' type to hold in the O ring was more successful than the current clip on one.

Glen

maybe daniel is correct about a bent housing.

did u swap over the housing when you installed the Mitsu locker??

I did , & couldnt undertand why I was going thru rear tyres like the were butter. They were wearing on the edges. took it to a truck alignment place & they confirmed it was bent!! Put my old housing back in with the locker installed & no more problems.

Would pay to get it checked out I reckon anyway.

cheers

Hi Ian,

I put my original housing back in (I changed housings when I bought the 4.9's with locking diff rather than just changing diff head as it is easier!) when I got the ARB.

So unless someone rolled my Pajero before I got it in a past life it will be straight. My tyre wear is normal on the rear. I put the original housing back in when I got the ARB as it has the right length axles for the ARB and had better handbrake shoes.

I guess I could try a truck alignment place. but I can't see it being the porblem....

Glen

So this diff was taken out again so that makes the 3rd time...
1st to be fitted
2nd to be checked and tighter than spec carrier bearings
3rd to check again, O rings under magnifying glass, tidy cut not visable with naked eye so replaced and put all back together


AND IT STILL LEAKS!!!!!


So it is now out for the 4th time!

The installer has done hundreds of air lockers and is about flumoxed. They must be some fragile O rings!