DIY VCU service

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Hippo said:
It's the "one wheel up test" and it's a measure of the resistance across the vcu. It's give us an analogue reading which varies from vcu to vcu. There are some vcu's where it won't give a reading but that's because the owner is too lazy to perform the test. Other than the "turnip test" there is nothing betterer than the "one wheel up test."

Reconditioners may advertise the test is bollocks, but they forget what they said when they ask you to drop by so they can use it to convince you to part with yer money when they test yer vcu with the same test.
Click to expand...

very true ,all lrs recon borg warner transfer boxes were tested with a torque wrench and stop clock
 
Hippo said:
It's the "one wheel up test" and it's a measure of the resistance across the vcu. It's give us an analogue reading which varies from vcu to vcu.
Click to expand...

Yes, anyone who's followed these VCU threads and thought about things must surely conclude that the 1WU test is the best way that anyone on this forum can test their VCU to any level of "accuracy". Adding a diluting agent into a stiff VCU does sound like it will bring 1WU readings back into a range that is safe and functioning.

What we don't really know though is how different the real operating forces/resistance are of a VCU that has had the 1WU test. Putting a 5KG weight on the end of a rod is not going to grind those disks inside the VCU with anywhere near the force that the engine will do. The engine will surely generate more heat in the plates and the original fluid is designed to lock with heat. Adding a diluting agent may reduce this, or it could even be a catalyst to stop its properties completely or make them more severe.

So...

The Mad Hat Man said:
tis all speculation and guesswork :p
Click to expand...

But great things have come from speculation and (educated) guesswork!
 
GrumpyGel said:
Yes, anyone who's followed these VCU threads and thought about things must surely conclude that the 1WU test is the best way that anyone on this forum can test their VCU to any level of "accuracy". Adding a diluting agent into a stiff VCU does sound like it will bring 1WU readings back into a range that is safe and functioning.

What we don't really know though is how different the real operating forces/resistance are of a VCU that has had the 1WU test. Putting a 5KG weight on the end of a rod is not going to grind those disks inside the VCU with anywhere near the force that the engine will do. The engine will surely generate more heat in the plates and the original fluid is designed to lock with heat. Adding a diluting agent may reduce this, or it could even be a catalyst to stop its properties completely or make them more severe.

So...



But great things have come from speculation and (educated) guesswork!
Click to expand...

The operation of the VCU is pretty clever. The real clever bit is the way it transfers the torque. If the speed difference between the plates is low, then the torque tranfered is also low. If the speed difference between the plates is high then the torque tranfered is also high. It's completely linear in operation, providing just enough torque to keep the rear wheels turning while needed. This is why the 1WU test works well as a test. The lever length and weight applied to the wheel hub nut gives a calculable torque figure. The VCU "sees much lower torque figure than that applied to the hub, this is due to the diff ratio. However it is turned faster than the wheel hub, again down to the diff ratio.
The 1WU test gives a good datum to follow. If performed at set intervals using the same test length and weight only the time requires recording. The longer the time to rotate the same amount, the stiffer the VCU.
 
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It's the "one wheel up test". You'll upset mad hat man with text talk bollocks.



To get round the differing lengths/weights issue the length and weight can be used to calculate force:

9.8 x length(in meters) x weight(in kg) = force in Nm

so for 1.2m and 8kg weight:

9.8 x 1.2 x 8 = 94Nm force applied

Compare time against force on a graph for comparison. Hence comparing the actual force against time to complete the test.

9.8 refers to gravitational acceleration and for the purists we're ignoring cos angle as we're using the force applied at 0 degrees which equals x1. The average force over the test is a constant factor of this so if we need it we can recalculate it later on we can without much trouble.

If the bar is 2m long and 4kg used:

9.8 x 2 x 4 = 94Nm

Measuring time against force on a graph takes out the difference of weight and length so it's more easily comparable.



I think it's a good idea owners try their own reconditioning. Owners in other countries do it.



The future of vcu testing as I see it...
I gave up pushing vcu testing at the beginning of this year. Far too many detractors compared to those doing the test. So why bother. It's gone on for years and the number of results we have are **** poor. My video is on permanent display around the world. You tube gives me view lists of countries and site names where it's linked to. Mostly non UK. They seem to run with what we're doing and actually apply it. How the fek they manage this I don't know. I watched my vcu results change as it started to fail. I then removed it when I felt I'd pushed it as far as I could. I have a replacement and have plans for my old one. I've tried many different tests to understand what my vcu was doing. One interesting one was to rig up the ability to measure the case temp whilst driving on and oft road. The case temp isn't a perfect example of what's going on inside but it does react to the test conditions and therefore is valid to a certain extent. You have to wipe mud oft the vcu regular but parking on an axle twister makes this easier. Another interesting test was to measure the rotational speed of both props to see the difference in speed whilst driving on and oft road. This varies on several factors like tyre diameter, driven surface and how the vcu is responding. It's true we can't apply the same levels of force to a vcu whist on the one wheel up test, which a driven Freelander can apply, but at least the one wheel up test is comparable in it's own form. Just think of the power a Freelander puts through a drive shaft. The kit I used to do this test costs several thousand £ but I think I can make something which effectively gives the same result, but for £12. Owners could then look at the values given and worry as it's nears 1:1 ratio. This would warn of tyre mismatch problems and tyre pressure too. But this is a project to look at again when time permits.
 
as above is what gave me the idea

(I think it's a good idea owners try their own reconditioning. Owners in other countries do it.)

after doing a google search and reading some of the efforts by others around the world i thought i have x2 naff vcu's sitting around doing nothing why not have a go my self no harm done to anyone
it is hit and miss fitting the vcu removing it and trying again i am getting quicker at fitting and removing it :D
as another thread i posted on i was going to cut one open clean and renew with fresh oil i may still do that if i can ever find the correct grade at the right price
removing the old oil into a measuring jug and replace with the same amount is not a problem
i tried many additive's with the old oil i removed none apart from pure silicon oil stayed and mixed constant
but in the end unless you try you will never know and i like to know one way or the other
Ron
 
Hippo said:
It's the "one wheel up test". You'll upset mad hat man with text talk bollocks.



To get round the differing lengths/weights issue the length and weight can be used to calculate force:

9.8 x length(in meters) x weight(in kg) = force in Nm

so for 1.2m and 8kg weight:

9.8 x 1.2 x 8 = 94Nm force applied

Compare time against force on a graph for comparison. Hence comparing the actual force against time to complete the test.

9.8 refers to gravitational acceleration and for the purists we're ignoring cos angle as we're using the force applied at 0 degrees which equals x1. The average force over the test is a constant factor of this so if we need it we can recalculate it later on we can without much trouble.

If the bar is 2m long and 4kg used:

9.8 x 2 x 4 = 94Nm

Measuring time against force on a graph takes out the difference of weight and length so it's more easily comparable.



I think it's a good idea owners try their own reconditioning. Owners in other countries do it.



The future of vcu testing as I see it...
I gave up pushing vcu testing at the beginning of this year. Far too many detractors compared to those doing the test. So why bother. It's gone on for years and the number of results we have are **** poor. My video is on permanent display around the world. You tube gives me view lists of countries and site names where it's linked to. Mostly non UK. They seem to run with what we're doing and actually apply it. How the fek they manage this I don't know. I watched my vcu results change as it started to fail. I then removed it when I felt I'd pushed it as far as I could. I have a replacement and have plans for my old one. I've tried many different tests to understand what my vcu was doing. One interesting one was to rig up the ability to measure the case temp whilst driving on and oft road. The case temp isn't a perfect example of what's going on inside but it does react to the test conditions and therefore is valid to a certain extent. You have to wipe mud oft the vcu regular but parking on an axle twister makes this easier. Another interesting test was to measure the rotational speed of both props to see the difference in speed whilst driving on and oft road. This varies on several factors like tyre diameter, driven surface and how the vcu is responding. It's true we can't apply the same levels of force to a vcu whist on the one wheel up test, which a driven Freelander can apply, but at least the one wheel up test is comparable in it's own form. Just think of the power a Freelander puts through a drive shaft. The kit I used to do this test costs several thousand £ but I think I can make something which effectively gives the same result, but for £12. Owners could then look at the values given and worry as it's nears 1:1 ratio. This would warn of tyre mismatch problems and tyre pressure too. But this is a project to look at again when time permits.
Click to expand...

You shouldn't get disenchanted Hippo. There may be some people questioning it but I'm sure most people (even those that originally question it) agree it the best way of testing a VCU that anyone's put forward yet.

I haven't put a rating up because I joined LZ when my IRD bust and I rebuilt it without drive to the pinion. I do intend putting it back to 4WD at some time, or adding to the stable with another that has working 4WD - so will post then :)

A rotational difference 'monitor' would have saved my IRD because I'm sure it and my VCU were healthy prior to 400 miles in 48 hours on an under-inflated tyre that I didn't pick up on (unless the VCU stuffed the tyre as well as the IRD). So in that respect its a great idea - one that MHM is a supporter of as well.
 
bugsb said:
......(I think it's a good idea owners try their own reconditioning. Owners in other countries do it.).....
Click to expand...

In Norway at least one owner does it :cool2:

Does it work? Yes.
In this country we have real winters so I think I would have noticed if it didn't.
 
If Reconditioning companies can buy the correct fluid, it must be possible for anyone to get hold of it. I doubt that landrover developed thier own special fluid or VCU, they would of used existing fluid, already developed, it would be alot cheaper.
 
LR didn't develop the VCU - they bought it (I believe) basically off-the-shelf from GKN - may have done some tweaking to its stiffness/fluid levels - but basically a standard product.

The reason its more likely that people overseas do their own VCU 'rebuilds' is because they are not easily/cheaply available like they are in the UK. We tend to have to get stuff like that shipped over from the UK and it costs a lot to ship something the weight of a VCU. You could of course buy a new one from the LR stealer at prices that would make a UK stealer blush.
 
bugsb said:
as above is what gave me the idea

(I think it's a good idea owners try their own reconditioning. Owners in other countries do it.)

after doing a google search and reading some of the efforts by others around the world i thought i have x2 naff vcu's sitting around doing nothing why not have a go my self no harm done to anyone
it is hit and miss fitting the vcu removing it and trying again i am getting quicker at fitting and removing it :D
as another thread i posted on i was going to cut one open clean and renew with fresh oil i may still do that if i can ever find the correct grade at the right price
removing the old oil into a measuring jug and replace with the same amount is not a problem
i tried many additive's with the old oil i removed none apart from pure silicon oil stayed and mixed constant
but in the end unless you try you will never know and i like to know one way or the other
Ron
Click to expand...

Nothing wrong with trying to fix your own VCU. If pure silicone oil is a remedy for thinning the thickened fluid. I for one will give it a go.
Well done for trying.
 
Last edited:
bugsb said:
i should add always measure how much fluid you remove so you replace it with the same amount
Ron
Click to expand...

Bugsb / Jonaf ,
Thanks for the great info, I'm definitely willing to give this a try, but still unsure of some details.
Can you advise:
- roughly how much fluid you had to replace.
- did you have a 'wheel up test result / bench test from before'
- how you decided that you had the right amount of fluid added is there a test result that we should be aiming for on completion ?.
I'd also be interested to hear which viscosity of fluid you used, where you purchased it and roughly what the cost was.
Jonaf, is see you have used 12,500 cst and 30,000 cst silicone, which would you recommend to give the best results.
Its great to see such a step forward on this problem in the last few days, DIY repair now looks achievable.
 
Found this on GKN`s website.......

These parts sounds interesting in the Technical features part....

:The degressive locking characteristics (viscous mode) can be tuned by fluid viscosity, number and size of plates, and fluid filling percentage.

:The “Hump” mode activation is tuned by the
fluid filling percentage.

They also have a service department, but no mention of VCU servicing...
 

Attachments

  • Viscous-engl.pdf
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cant promise i will get it done but if i get time tues i will open one up and measure how much fluid is inside i found that if i mix white spirit with the old silicon over 24hrs it all evaporates so i could in theory clean one out with white spirit leave over 24hrs and see what is left this may help others that want to try it
Ron
 
tkitt said:
Bugsb / Jonaf ,
Thanks for the great info, I'm definitely willing to give this a try, but still unsure of some details.
Can you advise:
- roughly how much fluid you had to replace.
- did you have a 'wheel up test result / bench test from before'
- how you decided that you had the right amount of fluid added is there a test result that we should be aiming for on completion ?.
I'd also be interested to hear which viscosity of fluid you used, where you purchased it and roughly what the cost was.
Jonaf, is see you have used 12,500 cst and 30,000 cst silicone, which would you recommend to give the best results.
Its great to see such a step forward on this problem in the last few days, DIY repair now looks achievable.
Click to expand...

The VCU contains approximately half a pint of fluid. I have not bothered to measure exactly because I adjust the stiffness by adding or draining fluid until the desired stiffness is obtained.
I think the viscosity should be 30.000 centistoke or maybe more to make it work more or less like the original.
Silicone fluid can be obtained from the representatives of https://www.dowcorning.com/
 
with me it was trial and error i drilled the holes removed x amount and replaced with pure silicon oil it takes some miles for it to mix in then the wheel up test if that fails you have to remove more and add more oil each vcu will be different
so its at your own risk
as was said on another post they use 30000 grade in r/c model cars doing a search you can buy the 30000 grade cheaper from a model shop from the USA depending on postal charges
Ron
 
Well ive finally drilled a hole in it:) I just in the process of letting some of the fluid drain out....when I first broke through with the drill I could hear gases escaping followed by the fluid and this was with the hole facing upwards....so it was definatly under some pressure in there....ive now got the vcu on the bench with the hole at the bottom....its slowly draining out...

I keep checking the resistance by turning it by hand...with a breaker bar....my aim is to remove some fluid and see if my vcu will loosen up a bit..I will keep removing fluid until I am happy.

Some pics as we all like pics:eek:

bubysabu.jpg

pa2enuhy.jpg

jereva3a.jpg

y2umene7.jpg

ma9ehe6u.jpg

de8ynu2e.jpg
 
I have sprayed brake and clutch cleaner in mine to break the ' sludge ' down as it was seized ! left it to soak for a couple of days with the holes covered up so it didn't evaporate too quickly , then let it drain for a couple of days , I can now turn it with ease with a 17mm spanner , there is still a little resistance there , but I put that down to bearings and friction of the plates !
 
I have come to this thread late so excuse any repetition , I have assisted my friend in refurbishing a VW-Audi VCU. It was done using a kit complete with all seals and silicon fluid and with a comprehensive guide I think the cost was around 50 euros.
The filling instructions required the use of a scale to measure the exact amount of fluid the tolerance was 25 milligrams + or - and was quite difficult to obtain with the viscosity of the fluid.
The VW, VCU unit was made to be serviced unlike the LR unit and once opened up and empty was simplicity itself the rotor blades were stuck with the casing into a dishwasher then reassembled with new O rings and then refilled.
If memory serves me I am all most sure that the fluid was a Dow corning product seem to remember rating being 30000.

I would imagine that the same system could be used when refurbing the LR unit scales before during and after will give a high degree of accuracy
 
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I think I have now reached termination velocity with my one hole and the fluid drain:(

Nothing is coming out now....im gona ave to buy a bearing puller to pull the bearing of so I can get the damper of so I can drill another hole to force the black tar out of my vcu..

I did a little test on the fluid that came out...and it seems that turps dissolves it:) only thing is I cant get any intothe vcu through my one hole.I pressume I need this other hole drilling..:)
 
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