Suspected IRD issue. Someone tell me I'm wrong!

dave21478 said:

Fck the fuses. As GF21 says, kill the ABS system totally - unplug the modulator and see what happens.

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+1 - there could always be a fault in the modulator itself, but disconnecting it completely will rule out all the other pieces - including the wiring to it.

With the repetitive/repeatable nature of the lockup at the same time as the ABS would normally activate itself, it would point to something in the ABS. If it were mechanical, I'd expect it to be a bit more random - and once locked, would remain locked until freed somehow - eg reversing a bit.

@MoominTD4 - once it locks up, if you turn the car off then start it again, will it then drive forward until you change to 2nd again, or do you have to free it up in some way? How do you know its the rear wheels that are locked up not the front all 4 or just 1?

dave21478 said:

Fck the fuses. As GF21 says, kill the ABS system totally - unplug the modulator and see what happens.

I would bet a reasonable sum of money its not an ABS fault. It will be a mechanical problem with the drivetrain. The abs light coming on is due to it detecting a sudden anomolous difference in speed between certain wheels as the rears lock up and its disabling itself as a safety measure. ABS is a fail safe system ie if and xhen it fails, it is still "safe" in that the brakes will operate normally without ABS assistance. Now there is always a chance of a freak occurence in the system causing it to brake the rear wheels but I find that rather unlikely.

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I agree. The ABS system doesn't apply the brakes anyway (although the related TC system can) - it can pulse the brake pressure that you apply rapidly rather like cadence braking. You could also eliminate the brakes as a cause by clamping off the flexi hoses to the rear brakes with some padded mole grips.

Okie doke, I've been at it again tonight, there have been so many posts on here in the mean time and I only have my phone to reply with and I don't want to seem ignorant so I'll just say that I'm grateful for all input as this problem has me perplexed at the mo.
I'd seen things like this before (not on freelanders) when I was a mechanic, but those were always attributed to the many universal/obvious issues which many people have already posted on here and diagnosed by following the usual fault finding path.
So, what I'll do is tell you what the car is doing, what I've done and where it stands now (because quite frankly this is going on a little longer than I'd hoped and certain commitments mean I can't be without a car)

As the car stands now:
Prop off so FWD only.
Starts and runs as normal, dash lights are TC, ABS, HDC. ABS is the latest and has only been on at the start of this issue (before the beginning of fault finding)
Car will go into gear and front wheels will drive.
The second the handbrake is released and you try to pull away both rear wheels lock. You can drag its lame arse end down a wet street and leave two skid marks. Both wheels are locked.
Jack up the rear and feel that both wheels are locked. Use brute force to turn the rear wheels by hand and they will move slowly, gradually easing up. Drop wheels and drums off and the hubs spin as normal, no grinding no excessive roughness.
CV joints are dry and the rubber seals are intact. A feel of the joint through the rubber says the joints are fine, diff mounts are also fine with no excessive movement.
Fasten wheels back on and everything turns as proper. Lower back to floor, get in, turn on and go to drive and you don't even get an inch of movement (yes, the handbrake is off)

*For reference: the problem originally occurred when car was moving (less than 20mph) now it is from the moment you set off. Problem was initially with rear N/S wheel locking and is now both wheels locking.
TC and HDC dash lights used to come on intermittently before this, they now, along with ABS are on all the time*

What I've done:
Checked all the mechanical bits at the rear from the outside I.e. not dropping the drive shafts or opening the diff.

Checked wiring for obvious breaks/trauma on all four ABS wheel sensors right up to the blue plugs and then as far up the car as I could trace the wires before they disappeared into a loom etc. Tracing the rear O/S one through the fuel pump housing led me to a black earth wire with a single female spade end which was seemingly attached to a tab on the fuel pump, but broke the tab due to rust when moved.
This was re made using a long length of wire direct to the battery (it was definitely earthed)

Tried car, still no go.

Removed 1x 5a fuse for ABS from drivers fuse box, removed 2x 40a for ABS fuses from engine bay relay/fuse box, removed big plug from ABS control module/pump/the bit the brake pipes run into inside drivers wing, all the above at the same time so that the ABS system is pretty damn disabled.

Tried car still no go.

In between each attempt to drive the car I have made sure the back wheels turn by hand prior to trying it under engine power.

I only have a cold, damp pavement to work on at the in-laws house with an indirect route to my tools with one side of the car on the road. Also because of having to get the bus I can only work on the car from around 19:30 till the neighbours kids go to bed (they don't like being woken up by lots of high velocity language and a revving diesel engine apparently)
No sympathy wanted, just wanted to state what I'm up against incase someone suggests *just* dropping the diff or driveshafts, using ten grands worth of diagnostic equipment or buying a donor car and swapping it piece by piece because frankly, now I've done what I have with the ABS stuff I'm leaning back towards mechanical failure.

So yeah, this is where I stand, holding the keys to a very comfortable paperweight.

If the hubs turn freely once the drums are off, we're looking at brakes, aren't we?

Here's what I would do:
1. Ensure the back wheels are free, then clamp off the flexi hoses, then test.
(Isolates hydraulic aspect of brakes, and checks for internal delamination of flexi hoses, which can act as a one-way valve)

2. If no better, remove clamps, back off shoe adjusters 10 clicks, then test. (Left one clockwise, right anticlockwise).
(Checks for stuck adjusters, corrects for lifted shoe linings and, to some extent, sticking handbrake mechanism)

3. If no better, remove drums, disconnect handbrake cables, use wd40 and pliers to free up handbrake mechanism on shoe hardware. Also check cables move freely in outers while an assistant works handbrake lever up and down. Remove shoe retaining clips, release shoes from lower bracket, and rotate hub so it has one stud at top and two at bottom. You will find the shoes and hardware can be removed as a unit. Check linings are not coming free from shoe backing. Clean and lube all pivots, and coppaslip bosses on backing plate. Before reassembling, check slave pistons move freely in bores. Test.

Inbetween each step, brew a good cup of tea, and think of every swear word you can. Aim each swear word at the car. Go on, call it a c*nt - you know you want to!

When you check the wheels turn, are both wheels off the ground? If so, once you get one wheel spinning, what happens when you stop the opposing wheel? Have you tried freeing them off then manually turning both in the same direction? (Obviously needs a helper).

Beginning to sound like the rear diff

Are the wheels locking even without pressing the pedal? If so, are the wheels locking, while the ABS modulator is disconnected, without pressing the pedal? In this instance, there's a simple test to eliminate the hydraulic system.
Simply crack off a bleed screw and check to see if that wheel now turns. If so repeat the operation on the other side. If cracking the bleed screw makes no difference, the fault is elsewhere. It could be the diff locking at random intervals or possibly the hand brake cables sticking, although HB cables wouldn't lock the wheels while in motion, without pulling the lever. It's not uncommon for shoes to de - laminate and lock a wheel, but this generally only effects 1 wheel, not both.

This sounds to me like an issue with the diff - it sounds like a major and terminal internal failure - I believe it is locking up under load (even the 'load' of the wheels driving the diff without the shaft.
The loud bang you heard was probably a part in the planetary part of the diff breaking.
Take the back plate off the diff and have a good look, and check the oil for contamination. I do not believe this is a brake problem at all. Everything you have described points to the rear differential.
I wish you luck.
It will - if above is proven - definitely need a new VCU. and you can only hope the IRD has not suffered. The strain applied to the transmission to cause such a failure is horrendous.

You haven't got a bit of carpet, or broken return Spring, or wiring loom acting on the brake switch when you press the clutch pedal have you?

I will be trying most, if not all of the above tonight, my dad is coming over so I have another pair of hands

I'm thinking diff too at the mo.

Planet gears were my first thought, but with the ABS light coming on it just piqued my interest in a different direction.

I also feared the VCU would need recon if the diff has blown so thanks for confirming that.
In that case, I'll probably replace the diff so I can get to work and back, but the VCU will have to wait.

If it does prove to be the diff, the ABS light could be caused by a damaged sensor at the rear where you have been working.

Gotcha.
Also, turns out my dad has a code reader (who knew!?) So that'll be coming over tonight.

Best of luck mate - I fear the diff is Captain Cooked.......
If so, the VCU caused the issue - ird failure prior to vcu - HIGHLY, unlikely, but possible , - different sized tyres ?? sometimes - but - again - unlikely - vcu failure most likely ! -.. either way. check the diff planetary - a CWP (Crown wheel pinion) would not cause a dual wheel lockup - Planetary gear assembly certainly could and would.
Loud 'bangs' are not usually brakes (meaning virtually impossible!) - classic transmission failure ! - fingers crossed it is ONLY the diff (AND VCU definitely needs renewing) - hopefully IRD is intact and has not suffered too much.

Again - I wish you well -

ABS light would illuminate if the rear wheels were locked and front wheels turned - I would not let that lead you into a false direction !

I was thinking diff until the OP said the hubs turned freely once the drums were off. As for loud bangs, ours can do this when the handbrake locks up (which it does now and again). Admittedly, this is mainly when the shoes suddnely release, but it has produced a series of bangs before as the brakes lock-release-lock-release etc.

Watching with interest...

I once jet washed the hippos wheels and the back brakes started to lock on.. Had to stop, reverse a couple of times to free em up..

I'd remove your brake shoes and try driving without them to prove the fault..

Then make sure all the bits are in the right place and nothings missing.. Once the shoes grab they self tighten on the drum due to physics stuff... You need to make sure the spring can pull them away from the drum again.

I'm not typing an essay today, I've been out too long in the cold.
You'll have to take my word for it, diff is goosed.
I'll fix it, put a used one on probably. VCU may get done if I can locate some dosh.
Thanks for the help folks, i'll stick a diff on and report back.

I feel for you - having a difficult to diagnose problem is a bugger.

It does seam strange that the power of the motor can't turn the wheels - but you can. Not saying you got it wrong - as you're the one with the car and you can see what's happening - just strange... so would imply that what ever the problem is, manifests itself when the car's on the ground.

For both wheels to have the same issue, you do have to think that its very unlikely that both would suffer the same fault at the same time, so therefore neither has a problem and it must be something else common to both wheels. That would point to the diff - maybe when you turn 1 wheel the diff will turn what ever ain't broke, but when 2 wheels (try to) turn (ie by the car rolling) it jams up.

The brake system is also 'common'. The hydraulics are on separate feeds and each shares a front brake - so you'd think that would rule them out - which would leave the handbrake. After freeing up the brakes - did you then apply the hand brake before then releasing it to drive off?

I'd be careful driving the car without brake shoes - you have to stop the car somehow - which can only be the brakes and I think you'd pop the cylinders without the shoes there.

Similarly, don't be tempted to drive the car without the drive shafts in place - eg to take the diff out of the equation - the hubs can/will fall apart. Might be an idea to remove the diff though and suspend the shafts on bungey cords or something to see how it goes - I don't know if this is possible - or just get a cheap diff from a breakers if you can find one.

Bugger - that'll teach me not to start a reply and leave it for a while before coming back!

It sounds like the diff to me, maybe a broken tooth/cog which would let the wheels turn but as soon as the oil gets stirred up by turning the wheels fast e.g. as in driving, all the bits gets thrown at the rest of the teeth jamming them

Ah well, at least you have a diagnosis. Two odd things:

1. Why could the hubs be turned once the drums were off? Perhaps the debris in the diff was floating around and causing an intermittent fault.

2. Normally with seized brakes, the wheel is locked solid (obviously). But with a diff problem you'd expect to be able to move the wheel a little by hand easily, while the wear/slack/backlash is taken up in the driveshaft and pinions etc., THEN encounter the seizure.

Looking forward to seeing some post-mortem pics of the diff (hint, hint!)

If money is tight and you are happy enough with 2wd for the meantime, remove the rear driveshafts. Split the outer CV joints and refit these in the rear hubs to hold the bearings together. The car will now be fine to drive.

ABS light on will be from messing with fuses and unplugging things. Once its driveable this should go out by itself after half a mile or so.