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Diff Problems.

Posted: 08 May 2020 23:03
by Andyhudson
I have a question. 4.8 GRX 2005

I switch the diff locker on in 4L, the light flashes and appears not to engage however it definitely feels like it has in fact engaged. Now the weird part, at first I thought it was perhaps the switch or a fuse but upon delving deeper, the bottom pipe on the solenoid is not sucking and I have tested switching the pipes around, it then engages fine. So if it’s not showing that it’s engaging (I.e it’s still flashing on the dash) and the solenoid is not sucking on the bottom pipe when it’s engaged, why is it still engaging, my fault finding has hit a brick wall. Even if I replace the solenoid, what difference would it make if it is actually engaging? It is definitely engaging as I’ve tested it on grass and dirt.
I have also checked all the cabling by the diff, re made all the electrical connections, tested the power going into the solenoid etc.

I’m stumped and run out of ideas so any advise would be very much appreciated.

Re: Diff Problems.

Posted: 09 May 2020 07:14
by Tinus lotz
What is your indication on the dash doing ?

Re: Diff Problems.

Posted: 09 May 2020 07:37
by Andyhudson
Both the ABS and DIFF LOCK Lights are flashing. The Diff Light doesn’t go solid as it should.

Re: Diff Problems.

Posted: 09 May 2020 10:24
by Peter Connan
I can't remember now which tube does the sucking at what stage.

It probably goes without saying that there will be vacuum on only one tube at any one time. One will suck when the switch is off, the other will suck when the switch is on.

If there is no suction on any tube, the locker cannot be held properly engaged. However, it is also not being held properly disengaged, and I guess there is a possibility that it can "lightly engage". The other thing is that, to me at least, driveline wind-up (due to being in 4wd) feels almost exactly the same as the locker being engaged. I think the only way to test whether the locker is working is to jack up both rear wheels, and try to turn one wheel.

Note that, if there is no vacuum on either tube, I would strongly advise not using the locker on any real obstacle. I firmly believe that it is under these conditions that the teeth get damage, which is what has given this system it's bad reputation.

Re: Diff Problems.

Posted: 11 May 2020 11:05
by ricster
I agree with Peter, I think ( but may be wrong) but if the locker is engaged, it probably is not fully locked in place. The diff lock is basically 2 square dog gear teeth that fit into their respective slots.The main reason the difflocks eventually "break is that the teeth jump out of their slots, rounding the teeth edges or faces making them even easier to jump out, so it gets progressively worse till it will not stay engaged. so as Peter said, one vacuum line will always be sucking, depending on the switch being on or off.
On mine I can hear a distinctive "clunk" (not super loud, but almost like the sound of a pistol slide when you cock it, but a little less metallic, more of a lubricated sound) as soon as the difflock fully engages or disengages.

Re: Diff Problems.

Posted: 12 Jun 2020 07:48
by johanp
I had the same problem that the bottom solenoid has no suction a few years ago.
To test if it is only the solenoid, switch off the difflock and the top solenoid should have suction.
Now put the bottom pipe on the top solenoid and your difflock should engage. If I remember correctly the difflock light will also light up when it is fully engaged.
To unlock you put the pipes on their original positions.

Re: Diff Problems.

Posted: 12 Jun 2020 08:37
by JohnBoyZA
ricster wrote: 11 May 2020 11:05 On mine I can hear a distinctive "clunk" (not super loud, but almost like the sound of a pistol slide when you cock it, but a little less metallic, more of a lubricated sound) as soon as the difflock fully engages or disengages.
Love the description - spot on :wink: :thumbup:

Re: Diff Problems.

Posted: 16 Jun 2020 17:54
by Izaakb
I agree with Johan p in my case one of the pipies sucked mud due to perished rubber connector pipes at the diff and ofcourse the vacuum. Currently i swap the pipes at the solonoid to engage my difflock but will have to replace the blocked steel pipe that is not that easy