W463 Centre Diff / ABS Issue
Morning all,
Looking for some more invaluable technical advice from the community.
W463 300GEL LWB
The centre diff is intermittently locking of its own accord. The centre diff light against the switch lights up red (no orange/amber light) and the diff does lock as you can feel the change in the handling. It seems to happen most commonly when on or near to full steering lock, but not always the case. When it locks, it also takes out the ABS, but perhaps this is standard when the diff is locked so is only a side-effect of the main issue.
Any suggestions please?
Well tackling the easiest issue firstly, it is quite normal for the ABS to be disengaed by default when the diff lock has been engaed.
Now onto the difficult stuff:
Does the diff lock engage at a particular full lock or at any full lock? Further, does the locking occur whilst in motion or can this be replicated at stationary full lock sceanario?
My initial thinking is taking me to go the diff relay but what to do after that, I haven' a clue. There have been isues with the diaphrgam but not sure how this could be, I'll need to look into further time allowing - Sorry for now.
Check vacuum pipes very carefully, there is one that is brown pipe I think ,connected by rubber near the battery . For some reason mine did the opposite and wouldn't engage, found to be faulty relay. If you don't need the centre diff I think you could remove the relay so no damage to transmission.
Think my vacuum pipe disconnected , centre diff lock took forever to engage, eventually burning out one relay
Been out in the G this evening and had the diff lock up whilst cruising along a straight road at 40mph so my attempt at spotting a pattern appears to have failed.
I'll check the vacuum pipes tomorrow and potentially remove the relay as a short term fix.
Thanks for the replies
There is definitely an issue there. You say it only engages at low rpms so it could be a split pipe and when it revs harder there is more vacuum. Does the centre diff light illuminate when its locked???
Heres one to try. Lock the centre diff and wait for red light to illuminate on switch. Then switch the centre diff off and stay at low revs while driving and weave from side to side a bit to take strain off so it can release. If it does not hold revs up a bit while rolling. If it comes out easier look for a leak on vacuum pipes or solenoid.
If diff engages properly every time on switch i would guess relay and solenoid might be ok
Hello Max,
I am sorry to say that this draft will not still help your predicament but my modus operandi for problematic issues is that it sits with me in the background and from vague memory of the electrical circuitry I have an incline that the ABS and Diff lock have some connection.
Now as you state the Diff lock engages or tries to engage at mostly full locks I beginning to wonder at full lock the wheels are under stress and should you have excessive wheel bearing play this could affect the ABS sensor some how. As a consequence of that a signal feed back to the Diff locks could occur?
Have you had any DTC (Diagnostic Trouble Codes) codes read?
I discontinue with vacuum pipes and checkings, for this part is only there to engage and disengage the diff locks it is not the sensory part of the system.
So no more forward in action but in thought at least. 
Ps - Check front wheel bearing play, please report back. My eye and attention is on thi sproblem and thread.
You could just turn ABS off and see if that has any affect. Tho have you been doing anything under the bonnet that may have accidentally knocked off a vacuum pipe? No hissing under the bonnet?
It will be something simple. Jason and myself have had similar issues. They were both a simple fix
Give us some more info on diff lock light coming on etc etc so we can have a better idea
Someone has asked me about a proper odd problem and i will post up when i get all the details. I have not heard of this before only on a motorbike lol
Read post properly
Red light is difflock engaged as you know. ABS is knocked out also which is normal
Relay or switch fault it probably is. Vacuum pipes split on a friends g wagon and it would not illuminate red light
Something is sending power to relay to engage or solenoid is defective. I would check there first
You could put a meter or connect a bulb to difflock solenoid or relay to see when and why it gets operated when it should not
Its always simple its just finding the cause. Dont know if you could swap relay for another diff lock relay and try it. If they are the same. Forget the pipes if all diff locks work ok and my apologies i did not study post well
If you get stuck come for a run out and i will check it over
Regards gaz
I
I agree with pistonhead also but a similar problem came from a split vacuum pipe on a previous vehicle
It would pull in the centre diff as soon as the vehicle was running. No light on dash though but diff was engaged all the time vehicle was running. Fitted new pipe and its still fine 5 years on
Basically check all of it. Simple system until it fails and needs fault finding
Thanks for the replies guys.
Pistonhead - front wheel bearings appear OK. I recently changed the shocks and springs and had a good fettle around the axles/hubs whilst under there and all seemed to be in order. This issue pre-dates the change of shocks and springs so was not caused during that process.
JASONGDS - I think the ABS is a side-effect of the diff locking rather than an issue in itself. There is no obvious hissing from under the bonnet. I've looked along the vacuum pipes several times in search of other problems and can't find any issues. When I manually switch the lock on it works as expected so I think there is probably enough pressure in the vacuum pipes for it not to be a problem.
g wagon g - I will look at the relays and switch. It is only the centre diff which this has happened to. Neither the front nor rear has ever been affected. The switches are obviously individual but do all three also have individual relays? I will look into this and swap one for another to see if the problem moves with the switch/relay.
Hi
Some have 3 relays that are the same part. Some have a different centre diff relay
Look on g 463 manual free download and study wiring
If you switch relays with fuse panel down you will see which ones click in for the 3 diff locks
If you remove the centre diff (transfer box one ) and your fault does not happen its either a bad relay or wiring issues i would think. Could be the solenoid but check them all before you purchase new items
If you were local i could lend you a relay to try
Keep me posted
Gaz
When it self locks does Amber light illuminate on switch? Or when you press switch it operates normally?
There are 4 relays I think , tho the main three are interchangeable, can't remember which does what but you should be able to feel it click when you press switch, think it's one of the four to the right that are all the same. 4th relay ( much bigger in appearance)is timer lag which is second from left, does red light stay on 20 seconds after you switch off? You should hear it release the pressure, attached is pic of vacuum switch for centre diff, can't remember exactly but you can disconnect something on the vacuum there that has effect of locking diff.Also I think?removing timer lag relay will mean no diff locks actuated, so if light still comes on, must be something internal on transfer box?
Very basic suggestion
Remove (temporally) the vacuum pipe from the top of the transfer case that activates the diaphragm and see if diff still activates.
With this move you will prove if its an electrical fault or inside the diff.
regards Tony
PS All the service info is available from the Members Area of the Website including a full rebuild of the transfer case!
I am still head and bum scratching on your issue in so far as I may throw some money for the reply.
Would you please furnish your chassis number and I just might need the registration number in which case either PM this to me or email it to me on:
Cheers,
Apologies for my delayed response, I've been away for the last week so no progress has been made. I've also got a few PM's to reply to on this so will get to you shortly.
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Thanks for the reply.
I'll experiment with stationary vs moving. I've only noticed it when moving, and quite often when in reverse rather than a forward gear, but has happened in both scenarios. Always at low speeds (as you would expect on an open steering angle). Reversing and wide steering angle tend to occur when reverse parking which is when it happens most often. So far the diff has not remained locked for long - 10's of seconds rather than minutes, and it will then release itself and return to normal without any input from me.
I'll attempt to replicate whilst stationary and report back.
Cheers