Testing Viscous Coupling Unit

When reversing with the steering on full lock there should be no additional load on the engine as a serviceable VC is relieving the stress in the drive train caused by the front wheels turning at a different rate to the rear wheels.

If there is load on the engine so that it wants to stall, or you have to use higher revs or the car feels as if the handbrake is still slightly on then the VC is not doing its job and there is transmission windup - a sign of a VC that has failed and locked up. The steering does have to be on full lock for this test to work. Some also say that the problem shows up in 'saw toothing' (whatever that means) of the tread on the tyres - my tyres have never had unusal tyre wear.

I have a 98 diesel and last week my VC coupling failed - my thread is about 6 down from yours. It then took out the IRD unit - very, very expensive so if you have doubts about your VC get it checked out because your IRD will also fail. If you have a pre 2000 Freelander the problem is the IRD (design fault with the differential ratio) causing the VC to work too hard causing it to fail which in turn causes the IRD to then fail. If your car is later than 2000 and you have a VC problem then the fault most likely lies with the VC itself but if it has failed it could wreck the IRD.

The Freelander section of http://www.ashcroft-transmissions.co.uk has some good information.

Hope this helps

Gazz

Hi,

After my experiences, I do it every 5000km when I change my oil. A lot of people say the rear wheel can be turned with your hands but in my experience that is not the case. When I replaced my IRD, I removed the driveshafts so had to replace the large nuts that hold the hubs on - so I had to buy a huge socket that fits.

When I do the test I don't need to remove the back wheel - I just remove the small plastic centre bits in the wheel and but my large socket onto the hub nut and with a large bar (mine is 2' long but a smaller one will do)apply steady pressure in a clockwise direction after the slack in the drivetrain is taken up. I have found that if you push in a jerky manner the wheel will not move but with steady force it does. If it moves the VC is OK if it doesn't stop driving and replace. The IRD will hold up for a while but will eventually fail - I haven't pulled mine apart but I understand it overheats with the loads placed on it and bearings fail and teeth and mesh on the pinion drive fail.

I have now droven 15,000 km with the new (second hand) parts and everything is OK.

Garry

Viscous coupling IRD Issues

Hi All, new to this forum but have owned 98 1.8 freelander for 6 months and have had to become instant expert on what it means to own an early Freelander. (Love the car in spite of it all!!!)
Had new (replacement) motor and new clutch in first month(98K km). Since then have discovered the wonders of LR's design job with the VCU and IRD. VCU is locked solid. Have dropped entire tail shaft out and using as two wheel drive pending some sort of resolution (to protect rear diff and IRD which although a little noisy still seem functional)
Seems to me the whole problem of locked VCU's, wrong front to rear diff ratio selection, IRD and gearbox destruction etc etc could be solved very simply by chucking out the VCU and replacing it with a simple manually switchable coupling in the tailshaft ie a single central equivalent to the old freewheeling/lockable front hubs on the old landcruisers etc.
I have been searching all the forums and while I seem to get plenty of agreement with the concept, no one seems to have actually come up with anything.
Any thoughts
Cheers
Ian Hughes
Tassie

When my VC failed I also ran around in 2wd but with the failed IRD still in place - it is the part that provides drive to the rear wheels that fails but if you get it early the metal particles do not take out the rest of the IRD.

When it happened to me I thought the same as you and searched but nothing came as an alternative - I decided that the best option would be to use the central locking diff out of the transfer case of a Discovery. I figured a housing could be made out of some thick walled steel pipe with appropropriate brackets welded on the outside. It would be bolted to where the VC is currently bolted with discovery universals and yokes welded to the end of freelander tail shafts.

This would give the freelander awd for onroad use and when the going got a bit ruff just activate a lever or push a button the lock the central diff to go to full 4wd. I have also been looking at how to fit in a dual range but the only space is in the gearbox where the front diff would have gone when the gearbox is used in 2wd rover cars - I don't think there is room - the other alternative would be on the end of the gearbox (like subarus have) where drive from the gearbox swithches back toward the centre of the car - there may not be room for this option and would require cutting the end off the gearbox and mounting a subaru dual range component on it.

Haven't found a wrecked Discovery transfer case to see if the first bit is viable and haven't found a wrecked freelander gearbox to see if the second bit is viable. With a decent engineering workshop both of these should be reasonably easy to do - it does require the courage and detailed planning and drawing.

To fix the design problems with early Freelanders you need to upgrade the IRD to post 2000 models as the ratios are all OK and do not wear out the VC. Another alternative is to make the VC a replacement item at 100,000 km so that the problem does not develop. An expensive option but will ensure the VC does not fail. I still have my failed VC and IRD lying around and when I have some spare time I am going to see why the fluid in the VC could not be replaced - that way you would replace the fluid every 100,000km rather than the whole unit.

Thems are my thoughts

Garry

Always to the point.
Early IRDs (lets say the one with wronf diff. ratios) was LR part no: TAG000020 and replaced by the TAG000230.
Bad news is none can tell us for sure which is the one that LR fitted to our vehicles and also the detailed differences between the two IRDs, but we suspect different (right) diff. ratios in the TAG000230 and maybe stronger bearings.
Its a crime from LR that still keeping us to darkness with that and plow a lonely farrow with rear wheel tests etc. Same attitude with the other issue named as Head Gasket Failure also known as HGF.
I'm not a car engineer, never been one, but with freelander im too close.

Back to the subject, my VC was almost seized last year and sometimes still wonder why.

One year after replacement im having signs that the my new VC working overtime. These signs are:
- high working temperature (im touching the VCs surface often to check),
- a feel of stiffer transmission when moving in the city with low speeds, changing gears etc.
- the classic uncaused tyre noise/strange tyre wear.

I think the best option for any owner with same symptoms is to change the IRD soon as possible with the new one (TAG000230) but the cost is really high, so we still play the game with the famous turn of a jacked rear wheel with 1st gear on and handbrake off and back again.

Also i never heard of an upgraded VCU.

ianann said:

Hi All (especially garrycol)
garrycol, Is there a simple way to check if second hand IRD I am looking at is the newer ugraded low VCU slip model (serial no on case, check the actual ratio of turns of input and output shafts etc) or one of the older high slip inducing models
Cheers
Ian Hughes
Tassie

Click to expand...

I cannot help with identifying which IRD is which from the numbers on the cases etc - as Hippo has said there are two offical part numbers but these do not seem to be marked on the actual IRD.

When I bought my new second hand IRD i put the two of them side by side and counted output turns vs input turns on each and compared them. Sorry - I did this 12 months ago and no longer have the specific details but will check at home tonite just in case I did keep the details. However - the gearing to the rear drive is the same on all the IRDs (makes sense or you would have to change gearing in the rear diff).

It is the drive to the front wheels that is changed. The later IRDs have higher gearing to the front wheels than the older ones, bringing the overall front gearing closer to the overall gearing of the rear, hence the VC is "less locked" and works less and hopefully doesn't fail.

In my L series diesel - 100kph was about 3200 rpm with the old IRD. With my new IRD 100kph is about 2700 rpm. The downside is that overall gearing is higher so offroad in first I don't quite have the pulling power I once did but this is not an issue for me.

Also, later IRDs have stronger bearings so that if the VC does fail there is less chance of damage to the IRD in the short-term. Transmission windup causes massive loads on the IRD bearings which get hot and fail - stronger bearings and more likely to take the load though the crown and pinion can also fail. The same thing happens with the rear diff but the IRD usually fails first - later diffs (different part number but the same ratios) also have stronger bearings.

I see you are in Tassie (Tasmania) - When my drive failed last year, costed new parts and it was not realistic to repair the car - I bought a matched IRD, VC and rear diff (only as a precaution as my old diff seemed OK) from a low milage TD4 from Triumph Rover Spares in Point Lonsdale in SA - cost was still substantial but a lot less than new. Car now cruises nice and easy with the higher gearing and gives a bit better fuel consumption.

Garry

Hippo said:

One year after replacement im having signs that the my new VC working overtime. These signs are:
- high working temperature (im touching the VCs surface often to check),
- a feel of stiffer transmission when moving in the city with low speeds, changing gears etc.
- the classic uncaused tyre noise/strange tyre wear.

Click to expand...

Even with the old IRD you should still get over 100,000km before the VC packs it in - as the VC does neet to slip a little to give 10% drive to the rear wheels on solid surfaces temps may always be up. Stiffer gear changing is a sign of transmission windup as is strange tyre wear. Do the check of reversing on level ground with the steering on full lock - there should be some binding but if the engine really labours or stalls like if the hand brake is on then I would be looking at the VC - as you have said there is still the good ole lift the rear wheel and turn test.

I have enquired with thye stealers and the GKN the makers of the VC about a more technical test - eg with the VC out of the car and one end locked there should be a range of torque settings to move a good VC but no one has a test apparently other than the symptoms we know about and the wheel test.

Good luck with it

Garry

hello Hippo and garrycol
I get the feeling I am talking two a couple of kindred spirits here.
I too am looking at buying a virtual standby drive train hence my specific interest in ratios and upgrades (in my previous message I of course meant upgraded IRD (not VCU as I mentioned))
Very early on (in my naivety)I asked the question about specific torque readings for good, bad and indifferent VCU. Whether LR dont give these figures on purpose I dont know, but got lots of responses about the rear wheel test which was nice to know but not really specific.
Wrt IRD and diff ratios I have received heaps of info from lots of helpful people but quite frankly it doesnt bear up under closer scrutiny when it comes to the nitty gritty of multiplying the ratios through.
Love the car to bits and am taking it as a (slightly obsessive) challenge to beat those b******s at LR design dept.
Cheers
Ian Hughes

VC update

I note many views of this thread but no more posts.

Does anyone know a more recent post with updated information?
Having thought a lot about this, I think by far the best work around is to remove the tail shaft and VC on older Freelanders. I have done this and my 1999 diesel has done 80,000 k with no trouble since the mod.
However I would like to be able to use 4WD occasionally.
My current thought is that free wheel hubs would be the perfect solution either on the front with the locked VC or prefererably on the back (like removing the tailshaft). Anyone know a source of Freelander free wheel hubs? Or a custom supplier who could build them? Or maybe a mod for hubs from another model?


Please post guys