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Intercept

Member Since: 27 Feb 2017
Location: Suffolk
Posts: 587

2002 Defender 110 Td5 Black LE Java Black

Td5 Diff Lock won't Disengage

At the end of a very wet weekend camping in North Norfolk most vehicles were unable to leave the muddy field. So I spent a few hours pulling various things out onto firm ground. No problems there - the difflock and TC did a great job. However, when I came to rejoin the tarmac to drive the 90 miles home I found that the difflock wouldn't disengage, despite all the normal provocation i.e. reversing/shunting for a while, reversing whilst at full steering lock etc. It would sometimes disengage, but would then soon re-engage within a few seconds. I was unwilling to risk driving that distance with the diff locked so got a recovery truck to take the 110 and Sankey comms trailer home.

Having spent the evening combing this forum and others for info, and a while poring over the (frankly not very good compared to the FC101 equivalent) workshop manual, this morning I ventured underneath to inspect the linkage. All looked present & correct according to the manual so I gave it a dousing with penetrating oil and proceeded to jack up a wheel to determine whether the diff was locked or the indicator was lying. The diff was indeed locked.

Returning to the pit revealed the cause of the problem:

Click image to enlarge

Click image to enlarge
The spring steel clip on the end of the big "n" shaped actuator linkage (the red part in the diagram) was fouling on the T case bolt on the right of the picture (indicated by the green arrow in the diagram). This was preventing the actuating lever from rotating to its full extent. Presumably this meant that it didn't reach the detent on the selector shaft inside the T case, thus allowing it to slide back into lock. It's a pretty crude mechanism, but now I know how it works, a 13mm spanner is all that is required to turn the T case shaft to lock or unlock the diff, and this could be easily done at the roadside.

Click image to enlarge
Now, I'm not a frequent user of diff lock, but I have used it several times in the last year, most recently during the snow a few weeks back. Engage/disengage worked fine then so it seems odd that it chose to misbehave this weekend. Nothing was seized - the penetrating oil was merely a precaution. It looks as though the "clip hitting bolt head" situation might be avoided via a few mm of washers under item 34 in the diagram below, but that shouldn't really be necessary if this linkage is to work on vehicles without. Alternatively perhaps the offending bolt (item 33) could be replaced with a lower profile part? Sadly I've not yet been able to remove it, as a 10mm open-ended spanner slips. And a 9mm won't fit. Could this be an imperial size?

Or is the fix as simple as item 36 being tightened up with item 34 in the wrong position? This might not be possible if item 30 has a locating flat on its shaft.

The diff is now unlocked via the spanner method but I'd like to ensure that it can't happen again. Has anyone else here experienced this? If so how did you fix it?

2nd Apr 2018 10:55pm

nosnibod

Member Since: 15 Aug 2007
Location: West Midlands
Posts: 370

1998 Defender 110 300 Tdi SW Bronze Green

It looks like item 34 has been fitted upside down if you compare the photo against the diagram... Dave
Green Goddess - 1998 Defender 110 300tdi

3rd Apr 2018 7:07am

VVS210

Member Since: 12 Nov 2016
Location: Hampshire
Posts: 953

Brilliant! - i had exactly the same problem back in the winter, hardly ever use diff lock but needed it off road & then couldn't disengage. Eventually got it off with a lot of wiggling the selector lever & haven't used it since. Now I have an insight into what to look for when it dries up enough for me to start crawling around on the ground with the spanners

3rd Apr 2018 8:01am

Caterham

Member Since: 06 Nov 2008
Location: Birmingham
Posts: 6298

2011 Defender 110 Puma 2.4 XS CSW Stornoway Grey

/\ definitely one of the potential problems although looking really carefully I think it is actually fitted the correct way round? ie the plate (item 34) should bend upwards away from the transfer box.

my 'itch' that took 7 years to find / resolve was related to the lever / linkage. effectively I'd move the lever into unlock but it was not quite achieving the full movement on the item 34 so although we tested it always showed as being in the unlocked position. anyhow the resolution was to loosen the bolts fixing the levers to the gearbox and move the assembly as far as possible (to the left if I recall) which meant the linkages moved item 34 that little bit further and just enough to fully push item 34 into the unlocked position where it would stay.

there's an obvious click when it fully moves into the unlock position.

if the above is the issue the short term fix is to remove the 'staple' that links 34 to the lever / linkage and see if you can manually push item 34 into the unlock position and leave it there for a few days to see if all is ok.

good luck. (and I hope above makes sense).

3rd Apr 2018 8:13am

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17390

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

Don't forget that if you are ever in the situation where you really can't disengage 4wd you can remove the front propshaft and drive quite safely with rear wheel drive only.

3rd Apr 2018 8:55am

Intercept

Member Since: 27 Feb 2017
Location: Suffolk
Posts: 587

Thanks everyone.

nosnibod wrote:
It looks like item 34 has been fitted upside down if you compare the photo against the diagram...

It is hard to see in the photo but it does bend upwards as per the diagram. Maybe another potential fix would be to remove it and bend it upwards by another 3mm.

caterham wrote:
the resolution was to loosen the bolts fixing the levers to the gearbox and move the assembly as far as possible (to the left if I recall) which meant the linkages moved item 34 that little bit further and just enough to fully push item 34 into the unlocked position where it would stay.

That could also be an option because the pivot of the 12" vertical link (with the "staple" at the bottom) has a thread and locknut arrangement to move the pivot horizontally.

blackwolf wrote:
Don't forget that if you are ever in the situation where you really can't disengage 4wd you can remove the front propshaft and drive quite safely with rear wheel drive only.

True. I pondered removing a prop but couldn't remember which one!

3rd Apr 2018 10:06am

Caterham

Member Since: 06 Nov 2008
Location: Birmingham
Posts: 6298

I have a tdci which I believe is a slightly different arrangement in so much that there isn't an actual means of adjustment.

my suggestion would be to remove the 'staple' and see if you can manually shift it at the transfer box into the unlocked position. if so you've pretty much found the issue.

3rd Apr 2018 10:13am

Intercept

Member Since: 27 Feb 2017
Location: Suffolk
Posts: 587

I can disengage it without removing the staple - just easing it upwards whilst moving the spanner in the photo is enough to get the T box to reach the unlocked detent.

3rd Apr 2018 10:16am

Caterham

Member Since: 06 Nov 2008
Location: Birmingham
Posts: 6298

aha.
so as it would appear in the photo. you need to lift it over the bolt head and hence that's what the problem is?

question - why has it become a problem (what changed)?

a few things to consider;

add a washer below item 34 to lift it over,
replace hex head bolt with dome head,
insert a spring over the 'staple' / along the staple between item 35 and the other end adjoining to main linkage which should lift the spring up so the end of it misses the bolt head,

hope you can get it sorted easily.

3rd Apr 2018 10:41am

JR

Member Since: 07 Dec 2012
Location: Auchtermuchty
Posts: 532

1984 Defender 90 200 Tdi SW Coniston Green

VVS210 wrote:
Brilliant! - i had exactly the same problem back in the winter, hardly ever use diff lock but needed it off road & then couldn't disengage. Eventually got it off with a lot of wiggling the selector lever & haven't used it since. Now I have an insight into what to look for when it dries up enough for me to start crawling around on the ground with the spanners

Whilst not doubting the reason shown at the top of this string, the more common reason for not being able to disengage the cdl is Transmission Wind Up. Wind Up is caused when the using Diff Lock when conditions may not fully need it and the rear wheels, which will take a shorter arc when cornering, are forced to turn faster/further than the actual line the wheels take; this is because the cdl locks the drive between front and rear and the front is prioritised due to the weight on these lead wheels.

If you've wound the transmission up going forward then you need to try unwinding it by reversing. Many try reversing a few feet, I've often had to reverse 150m or more before it disengages! We've also found that reversing on full left lock can often help....

3rd Apr 2018 10:48am

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 17390

Intercept wrote:

blackwolf wrote:
Don't forget that if you are ever in the situation where you really can't disengage 4wd you can remove the front propshaft and drive quite safely with rear wheel drive only.

True. I pondered removing a prop but couldn't remember which one!

It actually doesn't matter, either will do, but from personal experience I can say that the handling is a bit peculiar with front wheel drive (rear prop removed) but is reasonably normal and predictable with rear wheel drive only (front prop removed). The other consideration is that with the rear prop removed you will only have a handbrake if the difflock remains engaged or the vehicle is in gear. Disengaged the difflock and take it out of gear and it will run away even if the handbrake is hard on.

For this reason I would always recommend removing the front not the rear.

If you want a real surprise, try removing the rear prop, leaving the difflock disengaged and the handbrake hard on, and try driving off. You may be surprised at what happens! (Do not drive any distance though because you'll destroy the rather fragile centre diff).

3rd Apr 2018 11:22am

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