VCU Torque test results

I read it as the VCU slip ratio at 60 mph is 1 revolution per second? eg the plates in the VCU slip past each other at 1 rev/second?

Not the prop speed?

Here we go I will throw a spanner in the works, as I was not sure if my vibration was caused by the VCU not being very good, as told when I had the VCU bearings fitted.

I was getting very bad vibration before having the bearings fitted this then went to moderate vibrations, I then changed all break discs and pads added new break cables, I have let these bed in for a few weeks and I am still getting very slight vibration on braking ? so my next step of thought was to change the VCU front propshaft and rear propshaft.

I purchased GKN VCU front and rear shafts fitted them yesterday using the same mounts that was fitted by Bell Engineering as I was assured they are of good quality so did not purchase any new ones, will all the above fitted I can honestly say there is no difference in the drive of the FL 1 reversing or forward circle turning and I am still getting the slight vibration braking from 50mph to 0mph therefore it could not have been the VCU or shafts.

Very costly solution only to find the result is the same the only solace I can take from this is that I am a person that after I purchase a car I like to bring it up more or less new standards so the above would have been changes through age anyways.

I have yet to start my thread on what I have changed on this FL 1 since it was purchased in October last year but as I am an enthusiast it doe's not dishearten me, I am always in the frame of mind if you buy a second hand car you need to remind your self what ever you paid for it add another £1000 minimum to rectify any faults and from there constant preventive maintenance.

Now if I do a one wheel up test remembering that I have all brand new front & rear shafts new VCU bearing along with the new VCU and they are quality parts GKN what time am I looking to find from the test, can anyone person on here state this cheers Arctic2

jedi said:

I read it as the VCU slip ratio at 60 mph is 1 revolution per second? eg the plates in the VCU slip past each other at 1 rev/second?

Not the prop speed?

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If that's the case then the props are turning at approx 40 revs per second at 60mph.
So he would be saying the vcu slips 1 full rotation for every 40 turns of the props at that speed.
That would make the % difference between the 2 props 2.5% instead of 0.8% or 0.2%.
That's assuming perfectly matched tyres and driving in a straight line.

Arctic2 said:

Here we go I will throw a spanner in the works, as I was not sure if my vibration was caused by the VCU not being very good, as told when I had the VCU bearings fitted.

I was getting very bad vibration before having the bearings fitted this then went to moderate vibrations, I then changed all break discs and pads added new break cables, I have let these bed in for a few weeks and I am still getting very slight vibration on braking ? so my next step of thought was to change the VCU front propshaft and rear propshaft.

I purchased GKN VCU front and rear shafts fitted them yesterday using the same mounts that was fitted by Bell Engineering as I was assured they are of good quality so did not purchase any new ones, will all the above fitted I can honestly say there is no difference in the drive of the FL 1 reversing or forward circle turning and I am still getting the slight vibration braking from 50mph to 0mph therefore it could not have been the VCU or shafts.

Very costly solution only to find the result is the same the only solace I can take from this is that I am a person that after I purchase a car I like to bring it up more or less new standards so the above would have been changes through age anyways.

I have yet to start my thread on what I have changed on this FL 1 since it was purchased in October last year but as I am an enthusiast it doe's not dishearten me, I am always in the frame of mind if you buy a second hand car you need to remind your self what ever you paid for it add another £1000 minimum to rectify any faults and from there constant preventive maintenance.

Now if I do a one wheel up test remembering that I have all brand new front & rear shafts new VCU bearing along with the new VCU and they are quality parts GKN what time am I looking to fin from the test, can anyone person on here state this cheers Arctic2

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Sorry to hear it's still not resolved. Did you get measurements from the rear brake balance from the mot tester? I have to admit I didn't think yer vcu had problems when we tested it. Results should be similar to the link below. If higher then factors like rear brakes catching can cause times to increase. My guess is the vibration when slowing down from 50mph, which seems to happen around 20mph, is a vibration from the back, but only under hard braking. That's making me think the brakes are fighting at the back. Most peeps don't realise the vcu has 2 jobs. It's a balance between activating to provide more than normal drive connection through the props, which it doest when wheels spin or stop turning, or under heavy braking when the front tyres squash more so their radius (axle to ground distance) reduces and therefore the differing speeds of the props changes from normal. This has an effect on the vcu. Without having a LR test rig to capture it... the front prop speed would increase if the front wheel radius reduces and the rear wheel radius didn't. A new fred starting from the beginning of yer problems and what's been done so far my help trigger a response from someone who's had similar before.

http://www.landyzone.co.uk/lz/2141449-post246.html

Hippo said:

If that's the case then the props are turning at approx 40 revs per second at 60mph.
So he would be saying the vcu slips 1 full rotation for every 40 turns of the props at that speed.
That would make the % difference between the 2 props 2.5% instead of 0.8% or 0.2%.
That's assuming perfectly matched tyres and driving in a straight line.

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Now that sounds more plausable

You try turning a VCU 1 revolution in 1 second you would break something :rolly:

jedi said:

Now that sounds more plausable

You try turning a VCU 1 revolution in 1 second you would break something :rolly:

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2.5% is quite high though. I think it was more of a guess. We'd have more problems than we have if the % increased. I have tried turning a vcu as fast as I can. You certainly need to secure the other end.

Hippo said:

2.5% is quite high though. I think it was more of a guess. We'd have more problems than we have if the % increased. I have tried turning a vcu as fast as I can. You certainly need to secure the other end.

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Is this on or off the car ? can the car be lifted off four wheel gear engaged and then watch the VCU and shafts turning, if so as anybody tried this ? the VCU I took of was also a GKN and I really doubt there is anything wrong with it, are they of any value second hand ?

Arctic2 said:

Is this on or off the car ? can the car be lifted off four wheel gear engaged and then watch the VCU and shafts turning, if so as anybody tried this ? the VCU I took of was also a GKN and I really doubt there is anything wrong with it, are they of any value second hand ?

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If you run 4x4 with all wheels in the air the vcu will activate to turn the rear wheels all the time. Reconners buy vcu's. Some sell them one ebay.

Hippo said:

If you run 4x4 with all wheels in the air the vcu will activate to turn the rear wheels all the time. Reconners buy vcu's. Some sell them one ebay.

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Thanks for that another quick question for those reading this are the small discs on the VCU in the photo the right way round ? or should they be the other way please cheers Arctic2

Arctic2 said:

Thanks for that another quick question for those reading this are the small discs on the VCU in the photo the right way round ? or should they be the other way please cheers Arctic2

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Some pic's at the bottom of this fred:

http://www.landyzone.co.uk/lz/f69/freelander-1-vcu-bearing-replacement-how-guide-156068.html

Some don't bother with them but they do help protect the bearings from some splash.

Hippo said:

Some pic's at the bottom of this fred:

http://www.landyzone.co.uk/lz/f69/freelander-1-vcu-bearing-replacement-how-guide-156068.html

Some don't bother with them but they do help protect the bearings from some splash.

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Great so they are only used as splash guards and it doe's not matter which way round they are, well I hope not as I fitted them the way they came off when they were fitted at Bell Engineering, but yours seem to be fitted the other way round ? video of the VCU being spun round I doubt anything can be assessed by this but it seemed to run smooth ?


https://www.youtube.com/watch?v=hZAUFP8zX6E

Arctic2 said:

Great so they are only used as splash guards and it doe's not matter which way round they are, well I hope not as I fitted them the way they came off when they were fitted at Bell Engineering, but yours seem to be fitted the other way round ? video of the VCU being spun round I doubt anything can be assessed by this but it seemed to run smooth ?


https://www.youtube.com/watch?v=hZAUFP8zX6E

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It's best to fit them the way I (we do) so the muck spins out away from the bearing. Most would leave them as they are now they're on. Bearings tend to fail because they're cheap, but I get the feeling not all will have gone to the efforts you have to put them on squarely, which I believe will give them a longer operational life time.

Spinning on the bench seems ok. No noises etc. It's always difficult to tell. they spin much faster on yer hippo.

I got ****ed off again today by some know it all on Face ache sledging the 1 wheel up test. When I questioned why the test was "total rubbish" (his eloquent analysis without reason) his response was that is proven to be inaccurate (once again no reasoning) but did come back with "what is the torque required to turn the VCU through a gearing unit (diff)" - which in my mind might give different timings to non-geared test - but does not make it any less accurate.

So rather than putting up with his "30 years automotive engineering" knowledge - I thought I'd throw the question open to "proper engineers". I googled engineering forums and found 1 where I had absolutely no idea about what they were talking about and deduced that they must know a thing or 2. I therefore posed them the question - is the 1 wheel up test something we could rely on (especially in comparison to a workbench test).

You can follow the thread at ....

CR4 - Thread: Testing a Viscous Coupling

As expected, the response so far is the the 1 wheel up test is good and pukka.

Oh, and Hippo - you will grin when you see post #5!

Nice to see ma hippo is popular.

We've gained a lot of knowledge of vcu's over the years, but sadly this is plagued by the arguments about how it works and how to test it. I would be the first to admit the one wheel up test is not perfect, but it's the easiest test we have. Jack up one wheel and that's it. You don't need to take the wheel, props, vcu etc oft. So it's something most can do. The bench test is the best option but this involves removing the vcu which isn't something most want to do. It's also annoying if you want to test regular. Whilst the bench test is the best option... it's difficult enough to get peeps to do the one wheel up test which is much easier. I've bench tested my new one over a year ago but not got round to putting the video up. I've started going though the backlog of diagnostic video's I have so it will get done. I've also done the one wheel up test on it. The biggest problem with the one wheel up test is brakes catching or factors causing the transmission not to be as free moving as it should. If the results are high or worrying then peeps should try the bench test option. There's no science behind this... it's a cautionary option unless they find a reason why the test took longer like the brakes catching.

From what we know...
The vcu has resistance across itself all the time.
Resistance varies based on factors like heat and torque applied across it.
Turning a vcu is the only comparison we have available be it one wheel up test or bench test.
The torque turning the vcu on a FL1 when driven is far higher than what we can apply without a big test rig to support it all. I have tried this and my bnd workmate gambolled before the vcu turned.
The higher the torque applied to the vcu the faster it turns under our test conditions as we int applying enough torque to get it to seize up more than it is in standard form.
Turing a vcu a few revolutions is enough to mix the fluid around the plates, if the fluid is in good condition.
The turnip test (named after vagrent) is a quick test to see what the vcu's temp is. This is an indication of what it's been doing whilst driven on the road.
When I use the term "seize" I'm talking about resistance across the vcu. The vcu has a certain resistance across itself when normal, which increases when torque is applied across it. it's turned. It's doesn't seize solid when in use if it's in good condition, but it does tend to seize momentarily as it's resistance across itself oscillates due to the fluid properties rapidly changing.
Most peeps don't realise how quick to react a vcu is, and how much resistance it has across itself in normal condition, until removing it. Wheel spin when pulling away in ma hippo happens far more often without the vcu putting power to the rear wheels than when it's fitted.

My explanation of how the vcu works is over ere: http://www.landyzone.co.uk/lz/3080984-post22.html

I get a lot of pm's on ere and you tube regarding the test results. Ere's some of me favourites:

Wheel not turning = hand brake applied.
Wheel not turning = test not being applied to the wheel in the air.
Wheel spins too easily during test = vcu, props, rear diff or something in the ird missing.
Wheel spins too easily during test = too many wheels lifted.

I'm lucky that I spotted my vcu starting to fail, or at least taking longer on test which indicated something was changing. This was confirmed with a bench test. Some talk about eggspurts going for a test drive etc. This can be many miles or round in circles. Either way it's normally accompanied by builder talk: oooooo or breathing in through teeth, followed by emphasis on what they would do if it were there's. This normally ends in them selling you a vcu which you may or may not need. I feel sorry for those who only find out about it after their FL1 feks it's transmission.

If there is a definitive answer out there then I think it's still worth the effort to find it. I have to admit I've not been reading that many vcu freds for a while as I'm spending more time on diagnostic video's instead.

Long live the one wheel up test.

Hi all , been reading these threads with interest but the great has certainly worn-off - in fact I wish I never started.

Please forgive me if I've miss-read or there is an explanation somewhere but this test, surely with out diff-lockers on all your doing is prove that windup won't happen on your transmission system?

Silicone viscous fluid - From what I've read there is no evidence that this fluid will solidify. All I can find on the net about the degradation of a silicone fluid is that it will only happen with oxidation, which is unlikely in the sealed unit! (there are some oil company that are doing some research!!!)

So my understand is thus (from the guys on this site and interweb) the VCU is primarily there to protect the rear drive system from the brute force of power from the IRD (and maybe allow for slippage for motorway driving due to being in permanent 4x4??) so if the silicone and the plate within the VCU are to not fault is the culprit the bearing?

Can anyone please prove a VCU seizure, and/or Does anyone have a video of a seized or non-seized (slack) VCU?

Again please excuse any ignorance and this is not an intention stepping on anyone toes.

Note: The lengths people have gone to find out what's happening here is worth handshake, so thanks guys

SnapBrokeIt said:

Hi all , been reading these threads with interest but the great has certainly worn-off - in fact I wish I never started.

Please forgive me if I've miss-read or there is an explanation somewhere but this test, surely with out diff-lockers on all your doing is prove that windup won't happen on your transmission system?

Silicone viscous fluid - From what I've read there is no evidence that this fluid will solidify. The only way i can find on the net of the Degradation of a silicone fluid is that I can find is due to oxidation (there are some oil company that are doing some research!!!)

So my understand is thus (from the guys on this site and interweb) the VCU is primarily there to protect the rear drive system from the brute force of power from the IRD (and maybe allow for slippage for motorway driving due to being in permanent 4x4??)

Therefore rather than focusing on VCU as the culprit, surely is it not a bearing issue?

Does anyone have a video of a seized or non-seized VCU?

Again please excuse any ignorance and this is not an intention stepping on anyone toes.

Note: The lengths people have gone to find out what's happening here is worth handshake, so thanks guys

Click to expand...

Rest assured the VCU's on Gaylanders and P38's do seize.
On the Gaylander, the VCU is what engages rear drive when the front wheels lose traction, it transmits virtually no power as long as front and rear wheels rotate at the same speed which is why evenly worn tyres front to rear is so important to preventing over stressing the VCU.

This is how they do-it on a VW with T3 syncro - sorry it only in German....

https://www.youtube.com/watch?v=slujJmXoSAo

Thanks Datatek's.

SnapBrokeIt said:

This is how they do-it on a VW with T3 syncro - sorry it only in German....

https://www.youtube.com/watch?v=slujJmXoSAo

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What has that got to do with a Gaylander?

SnapBrokeIt said:

Please forgive me if I've miss-read or there is an explanation somewhere but this test, surely with out diff-lockers on all your doing is prove that windup won't happen on your transmission system?

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The test is there essentially only to test for wind up - when the VCU should not wind up the transmission.

SnapBrokeIt said:

Silicone viscous fluid - From what I've read there is no evidence that this fluid will solidify. All I can find on the net about the degradation of a silicone fluid is that it will only happen with oxidation, which is unlikely in the sealed unit!

Click to expand...

I'm not sure if anyone on here knows why the VCU tightens. Your research that silicone fluid will only solidify with oxidation may be correct. However there are various other factors in play. The silicone fluid is a generic base product. There are many different products based on silicone fluid/oil of which the product used in VCUs is just 1 - or maybe 2 or 3 depending on manufacturer. So the mix that goes in VCUs may be liable to get thicker for other reasons - eg repeated heating. There is also a lot of friction against the plates in a VCU - this is how it transmits power. This friction causes wear and the fine particles worn from the plates mix wit the fluid and contaminate it. This changes its properties.

SnapBrokeIt said:

So my understand is thus (from the guys on this site and interweb) the VCU is primarily there to protect the rear drive system from the brute force of power from the IRD (and maybe allow for slippage for motorway driving due to being in permanent 4x4??) so if the silicone and the plate within the VCU are to not fault is the culprit the bearing?

Click to expand...

Freelander is not Permanent 4WD - it is All Wheel Drive - AWD. The VCU is not there to protect anything. It is there to provide drive to the rear wheels when the fronts lose grip - period.

SnapBrokeIt said:

Can anyone please prove a VCU seizure, and/or Does anyone have a video of a seized or non-seized (slack) VCU?

Again please excuse any ignorance and this is not an intention stepping on anyone toes.

Note: The lengths people have gone to find out what's happening here is worth handshake, so thanks guys

Click to expand...

The VCU does not need to sieze to cause damage to the transmission - just tighten sufficiently to cause damaging levels of wind up to the transmission components.