My VCU help please

austen said:

Or if you fancy a bit more excitement jack both rear wheels up and try and drive away, if it has got front wheel drive it will get interesting

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I like that test - we ought to promote it more

Hi all, i am in the same boat,found out this morning while attempting to drive up a hill with 6 inches of fresh snow,rear end came round and i saw rear wheels turning only,tc was showing on dash,rear n/s wheel turns, only owned for 3 months and this is the first time i have needed it. I have emailed bell eng.

What is the problem,gearbox or other?

Ifeel like the proud owner of a chocolate teapot

Post in the introduce yourself, then come back and read all of this thread!

I have read the thread prior to my intro,i have the same problem as kaye and i have read all opinions,but was austen's theory the one or the cv joint,that is all i am trying to find out because i have no transport based on this, and it is very important for me,i only owned it for 3 months.never had a 4x4 and today i found out i still don't. I have a 2 wd and they're the wrong wheels doing the hard work. I am after a bit of help from people who know more than i.

at the risk of repeating myself ad-nauseam on here - do a VCU check as in the FAQ section - & yes - :search:.
when yu do that you can see if its the VCU that splits the drive or whether the prop turns up to the IRD - cant you? Once you have done that, report back with detailed results and we can help further.
You need to help yourself as well, you know.
My betting is on IRD.

austen said:

If you only have drive to rear wheels there are 2 possible reasons. The most common reason is the spline in the gearbox has sheared so only the one shaft is being driven to the IRD. This requires a new part differential in the gearbox itself, they are approximately £170 for the part,lus the fitting (gearbox out job). The other cause which is very rare(only really ever seen it once), are the small gears inside the IRD which can bee seen through the fill plug has bee worn away/sheared off. This requires a replacement IRD unit. This is very rare though as it usually results in the the IRD being smashed up as the teeth are sheared off.

This fault is nothing to to do with your VCU, if you remove it you will find the car will not even move forward. But the problem you will have if you fix the gearbox/ird, if the vcu wasn't buggered before, driving it around with only rear wheel drive WILL have ruined as it will have been over heated.

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I'm going with this answer above

The Traction Control get's weird if the rear drum brakes are out of adjustment (the auto adjuster is shyte), and can be overwhelmed if all 4 wheels loose grip

and, the knocking heard on gearchanges from the back is the rear diff bushes.


When all is working, I have found this to be just about the best vehicle on snow/ice/wet grass. And I've had a few of all the Land Rover varients and the "opposition"

The Mad Hat Man said:

...when yu do that you can see if its the VCU that splits the drive or whether the prop turns up to the IRD - cant you? .....

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The VCU doesn't "split" the drive like a transfer box.

All drive comes out of the IRD - 2 front wheel drive shafts and then a rearward prop to the VCU which is always spinning on that end.
When the VCU locks up, drive then travels to the prop on the other side and onwards to the rear differential

Never heard that one about the rear drums, interesting!

ffs - it splits the drive from the front prop to the rear

if he does a vcu test and the front prop spins like it aint attached to the ird, then the chances are the IRD is buggered.
If the front prop dont turn, but the rear one does, then the VCU is working something like propper.

The Mad Hat Man said:

ffs - it splits the drive from the front prop to the rear

if he does a vcu test and the front prop spins like it aint attached to the ird, then the chances are the IRD is buggered.
If the front prop dont turn, but the rear one does, then the VCU is working something like propper.

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The way you wrote it didn't explain what you meant ..ffs

Mark2 said:

The VCU doesn't "split" the drive like a transfer box.

All drive comes out of the IRD - 2 front wheel drive shafts and then a rearward prop to the VCU which is always spinning on that end.
When the VCU locks up, drive then travels to the prop on the other side and onwards to the rear differential

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I thought i was being really stupid asking for some help ( tech, not someone to come round and do it for me) and what a welcome !
I'd better start using my feeble brain....
Right, the ird unit distributes drive to the front and rear wheels,the drive to the vcu is fine because the rear wheels would not turn if it was kaput
The front wheels dont turn so i think the ird drive to the front wheels is at fault ,how can front drive be lost

So how does that happen,no negative comments reqd.
Thanks for your words Mark2.

Hairy65 said:

I thought i was being really stupid asking for some help ( tech, not someone to come round and do it for me) and what a welcome !
I'd better start using my feeble brain....
Right, the ird unit distributes drive to the front and rear wheels,the drive to the vcu is fine because the rear wheels would not turn if it was kaput
The front wheels dont turn so i think the ird drive to the front wheels is at fault ,how can front drive be lost

So how does that happen,no negative comments reqd.
Thanks for your words Mark2.

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accept the negative comments as well - or no comments .

firstky you are wrong in your premise here - "the drive to the vcu is fine because the rear wheels would not turn if it was kaput".

firstly the VCU is supposed to only lock up when the "slip" between the front and rear props reaches a pre-determinate limit. - see the "how a VCU works" thread.
if the VCU has failed, it can fail in one of two ways - see the "how a VCU works" thread.
1) siezed up.
2) no drive transmitted thru.

If it fails as per 1) then it will put a huge strain on the complete drive train. the first thing to go is usually, but not always, the IRD.
If the IRD has gone, it is possible to continue to drive the rear, but not the front.
If it fails as per 2) then it will never transmit drive to the rear and so you will get the front wheels spinning.

I suggest you read more or take the advice on here.
First thing to determine is what state your VCU is in - hence "test the feckin' thing"

Enough with the ffs,THE FRONT WHEELS DONT HAVE DRIVE, THE REAR DO SO THE VCU IS FINE I DON'T NEED TO LIFT THE CAR UP TO KNOW THAT !!!!

I want to know what to do with the ird if it is not allowing drive to the front wheels,is it dead or is there a fix so i can get my butt to work cos i don't have a fleet of cars to pick from.

Hairy65 said:

Enough with the ffs,THE FRONT WHEELS DONT HAVE DRIVE, THE REAR DO SO THE VCU IS FINE I DON'T NEED TO LIFT THE CAR UP TO KNOW THAT !!!!

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absolute Bollix!!

I give up - if you know it all - then fix the bloody thing - I'm orf .

Ignore me i'm feckkin fed up.

I can take advice,it just seems like i'm getting talked to from the off as if i were a 5 yr old,meanwhile there have been 4 differing opinions which lets face it, aint assisting my predicament one iota,i will test when i can get under my piece of crap which is stuck in a kin snowdrift cos the wheels aint turning, SOD THIS,I'M OFF TO THE PUB!!!!!!!

When i get back from the pub i'll fix it with a sledgehammer !!!

Hairy65 said:

Ignore me i'm feckkin fed up.

I can take advice,it just seems like i'm getting talked to from the off as if i were a 5 yr old,meanwhile there have been 4 differing opinions which lets face it, aint assisting my predicament one iota,i will test when i can get under my piece of crap which is stuck in a kin snowdrift cos the wheels aint turning, SOD THIS,I'M OFF TO THE PUB!!!!!!!

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I know feck all about VCUs and IRDs (I dunt even know what an IRD is ).... but if I wuz gonna take advice.... I would read what Mad Hat Man has said again.

Point taken,too many opinions clouding the subject ,who's right ? I don't know who the wise one is, i just got here.

We're all right, you need to help us help you by narrowing down your cars problem.

The IRD can drive the rear without driving the front if it is damaged. If this is the case the IRD is toast and needs repair.

The VCU, which doesn't lock up or seize btw, can get stiff to the point it winds the trans mission up and dameges the IRD.If this is the case your VCU is toast and needs replacing.

If you don't test for these how can you know what to do next.

I realise this can be frustrating, but i've had to do it and just about everyone that's posted trying to help has as well.

Hoyt-Protec said:

We're all right, you need to help us help you by narrowing down your cars problem.

The IRD can drive the rear without driving the front if it is damaged. If this is the case the IRD is toast and needs repair.

The VCU, which doesn't lock up or seize btw, can get stiff to the point it winds the trans mission up and dameges the IRD.If this is the case your VCU is toast and needs replacing.

If you don't test for these how can you know what to do next.

I realise this can be frustrating, but i've had to do it and just about everyone that's posted trying to help has as well.

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wot he said ^^^^^^^^^^

the chances are its the IRD thats buggered, hence only drive to the rear, but if the VCU is also siezed up, then replacing the IRD will be very shortlived.
Hence check the VCU first, coz its the easiest to check and then the IRD when yu know whether the VCU is gonna **** up a new IRD or not.