Diff lock switch replacement

[ChristoSlang]

Klink of daar te min vacuum is wanneer jou kar idle, en wanneer jy ry weer genoeg om die locker te laat inskop? Maybe te doene met die nuwe enjin wat minder vacuum op idle het?

PS: Wees versigtig om met 'n diff wat ge-lock is op 'n teerpad te ry - iets gaan breek wanneer jy 'n draai probeer vat

[Alex Roux]

Dankie vir die waarskuwing.

Ek was nie gelock op die teer nie. Ek het net gaan ry om die indicator se liggie te toets in sy unlock posisie

Maar dit is 'n belangrike punt wat ek nog nie goed verstaan nie.
Selfs op die sanderige stukke op die baan unlock ek elke keer voor ek draai.
Ek is paranoies oor die spanning wat ek op die as plaas. Presies hoe versistig behoort mens te wees?

[Peter Connan]

Alex, be very carefull.

There are effectively two vacuum systems at work here. The one locks the diff, and the other keeps it unlocked.

Thus if Christo's suspicion of insufficient vacuum is correct, then that means that the diff lock is not actually locking, but is not properly unlocked either. This is the best possible way to destroy the diff lock completely, because it will keep chipping the teeth away.

I think you need to measure the vacuum pressure of your system and compare it to a Patrol with a Patrol engine's, but i don't know of somebody with the required vacuum gauge.

I guess there could also be a leak in the diaphragm (the actuator on the diff that actually moves the diff lock parts), as this might show similar symptoms. this should be easier to test. Unplug the two hoses at the diff with the engine running. Feel or hear which one has vacuum present, and plug it back in position. Now place your finger over the other port of the actuator (the steel pipes at the diff, not the rubber hose), and feel if you can feel any vacuum. If you can feel nothing, double-check by placing some spit on the pipe and seeing if it remains there or pops (like you check a tire's valve for leakage).

I beleive that water in the diff can be discounted as being the problem, I can't see it causing this problem.

[ChristoSlang]

Alex, Peter's test for a leaky diaphragm is spot on

I tried to upload two photos showing the chipped away gears inside my Patrol's locker, but the forum replied with a "Sorry, the board attachment quota has been reached."

Any way, the Patrol's locker has a gear with only two big teeth that engage into another with 6 available slots. Even when the vacuum works as intended, this design allows a slipping drive wheel to spin quite a bit before the locker actually engages. This is obviously not an optimal situation. In contrast an ARB locker has about 40 corresponding splines, so the rotation before it engages is significantly less, with a subsequent reduction in stress when it does lock.

The scenario above assumes the vacuum works well. But when the Patrol's vacuum circuit is not working perfectly, the diff never gets a chance to engage fully and those teeth just end up mashing helplessly against each other. This is what happened on mine. By the time your diff has failed to engage a couple of times, it may already be beyond repair

Peter is the mechanical engineer, I'm sure he'll be able to comment further on the pros and cons of the various designs. I'll try to be clever when you encounter an electrical fault

[Grootseun]

Pieter , ive got the neccesary gauge , ill measure the vacuum tonight when swambo brings the troll home

[Alex Roux]

Grootseun

Can we then compare your measure to mine on Saturday at SAC's?

[Grootseun]

Ok ill bring the vacuum gauge along and we can test it there

[Alex Roux]

Alex, be very carefull.

There are effectively two vacuum systems at work here. The one locks the diff, and the other keeps it unlocked.

Thus if Christo's suspicion of insufficient vacuum is correct, then that means that the diff lock is not actually locking, but is not properly unlocked either. This is the best possible way to destroy the diff lock completely, because it will keep chipping the teeth away.

I am the furthest thing away from a mechanical engineer, but this system does not seem like the best piece of engineering?

So this may sound silly, but what exactly can I do if I want to be careful?
I understand the problem, if it is not properly unlocked, it chips away as I am driving, right?

The guys at Mmcarthy Nissan are hopeless, so no point going to them. I any event they are likely to charge me a fortune for something that is unlikely to be the source of the problem - as I have experienced thus far...

[Peter Connan]

Alex, I have probably overstated the case slightly, but I would recommend temporarily disconnecting the tube that would normally engage the diff lock, and blocking it off so that goggas don't nest in there.

The system is not perfect, but no factory-fitted difflock is perfect. All are prone or at least accessible to some type of damage or malfunction. As factory-fitted systems go, I beleive only the Steyr Puch's and perhaps the Unimog's (and maybe the G-wagon) systems are significantly better, and I certainly think the Patrol's is better than Toyota's system with the electric actuator in the diff (yes, I know, I am ellergic to electronics).

The Patrol's system is probably the part of the vehicle most prone to malfunction, but that is only because the rest of the car is so bullet-proof. It is also a system that is generally speaking easy to diagnose and fix. It does however respond best to regular use, and I strongly recommend that you use it at least monthly.

The ARB system is certainly stronger, but is also vastly more complicated and expensive. Also, if you over-stress the ARB system, you generally end up with a broken side-shaft, leaving your vehicle effectively stranded. With the standard system, you break just the diff lock. You can continue your journey, and it should at least in theory be less expensive to fix. But if the system is working correctly, and you use it with due care, it doesn't break that easily.

By the way, Wimpie's patrol (which has ARB diff locks front and rear) has an air leak on the front locker, so the ARB system is not foolproof either.

[Alex Roux]

Hi Peter

All noted and thanks.
At least the rest of the chassis is sort of bullet proof, and I gues there is merit in having a link in the system weaker than the side shaft, i.e. the diff lock becomes the "sacrificial lamb" to break before more serious damage occurs.
I have seen Wimpie drive, and he has no mercy with his Patrol. So I am not surprised of a malfunction...