I'm planning on making a mechanical replacement for the VCU!

OK, as you buggers in the UK have all p****d off to bed by the looks, something for your morning cup of tea. I'm sure "pressure" is a much better indicator of stresses (or lack of) caused by a VCU "going tight" (or unlockable). I believe though that it would be difficult to test for - but if there's stress would that create heat in (say) a bearing on the crown/pinion wheel? If it does, it would once again be difficult to detect it inside the IRD, but could a temperature sensor be mounted on the outside of the IRD casing where one of these bearings is mounted? Would a detectable amount of heat (change) be created by a tight VCU when it should slip and that heat permeate through the IRD casing to be detected?

Checking the temperature of the VCU itself is not a good idea - firstly because its spinning so would make it difficult, but also what the VCU is supposed to do in relation to heat and what it actually does - may be 2 separate things.

wrong!
how would measuring "pressure" determine whether the VCU was working correctly. Measuring heat wouldnt show much as it is heat that makes theVCU operate. Lack of heat might be an indicatore, but as I stated before, measuring the difference in rotational speed of the two halves of the VCU would give a more meaningful measurement because one that gave little or no slip would give little or no variance and one that slipped all the time would give a high variance. More importantly though, either woukd be a relatively constant output. If a VCU was working correctly then the variance would be changing irregularly. This would be easy to ascertain with non contacting sensors too - a problem with most feedback systems.

But

and its a big BUT, whatever system woukld need to be cheap and reliable, otherwise it might be cheaper to change the VCU more regularly.

The Mad Hat Man said:

wrong!
how would measuring "pressure" determine whether the VCU was working correctly.

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Because whether the VCU is slipping or not is not what damages the drivetrain. It is when it doesn't slip when it should do that does. Therefore the way to tell if the VCU should slip is by measuring the pressure it is applying to the transmission.

Its a bit like the 1 wheel up test - that measures the force needed to slip the VCU when the car is stationary - which is in effect the pressure the VCU is applying. Obviously you can't do the 1 wheel up test when driving down the M1 - but if you could measure the pressure its applying to the transmission, it is essentially the same thing.

The term in the 1 wheel up test is 'force', I termed it 'pressure' - they may technically be different things - but that's what I'm meaning.

A correctly working VCU will only exert so much force/pressure on the drive train when turning, a tight one will raise that force/pressure - so the bearings fail and teeth get stripped.

The Mad Hat Man said:

Measuring heat wouldnt show much as it is heat that makes theVCU operate.

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Agreed, that's why I mentioned not testing the VCU.

The Mad Hat Man said:

Lack of heat might be an indicatore, but as I stated before, measuring the difference in rotational speed of the two halves of the VCU would give a more meaningful measurement because one that gave little or no slip would give little or no variance and one that slipped all the time would give a high variance. More importantly though, either woukd be a relatively constant output. If a VCU was working correctly then the variance would be changing irregularly. This would be easy to ascertain with non contacting sensors too - a problem with most feedback systems.

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Yes, you could measure the rate of slip, but you would need to analyse what was causing the slip and whether it slipped sufficiently before tightening to apply damaging force/pressure on the transmission.

That's why I'm thinking to measure the force/pressure, either as a guage or when it exceeds a damaging level, throw up a warning/LED. It may be that damaging levels are different for short durations (eg turning or pulling away off road) and long durations (eg open road)

The Mad Hat Man said:

and its a big BUT, whatever system woukld need to be cheap and reliable, otherwise it might be cheaper to change the VCU more regularly.

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Absolutely - regardless of whether its a "VCU Replacement" or "VCU Monitoring", its got to be cost effective. If you could "measure" it, it wouldn't just save expensive repair bills, but could save on replacing the VCU when its still OK, and give you warning when it's getting towards the end of its life so you can plan for it financially.

The costing side of it is why I was wondering if you could tell the force/pressure exerted on the transmission by the temperature of a bearing and then whether you could cheaply mount (glue!) a temp. sensor on the outside of the IRD/Diff case by the bearing to pick it up.

Good luck.
I can't see that it will be an easy mod or cheap.

The method I have suggested is cheap, easily manufactured, has no direct contact to the VCU, can be mounted to the body of the vehicle and gives an easy guidance. It also has the benefits of being as "smart" as is wanted.

Lidl are selling bike computers at the moment..... I guess that these could be used to monitor the prop speed variance for not a lot of gold!

omg ive just read 11 pages only to find someone was right about 10 pages back that it probably aint worth the hassle. wish he'd have come up with something though, more for additional peace of mind but as been stated, think i'll just replace vcu and take care of my tyres, less grief/cost in the long run

craigmidlands said:

omg ive just read 11 pages only to find someone was right about 10 pages back that it probably aint worth the hassle. wish he'd have come up with something though, more for additional peace of mind but as been stated, think i'll just replace vcu and take care of my tyres, less grief/cost in the long run

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Yup......

craigmidlands said:

omg ive just read 11 pages only to find someone was right about 10 pages back that it probably aint worth the hassle. wish he'd have come up with something though, more for additional peace of mind but as been stated, think i'll just replace vcu and take care of my tyres, less grief/cost in the long run

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Did you read the other 11 page threads on the same subject that come to the same conclusion on their first page

craigmidlands said:

omg ive just read 11 pages only to find someone was right about 10 pages back that it probably aint worth the hassle. wish he'd have come up with something though, more for additional peace of mind but as been stated, think i'll just replace vcu and take care of my tyres, less grief/cost in the long run

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It's only three pages long and somebody told him on the first page it wasn't worth it...

No I just stumbled across this thread lol

TorqueTrak 10K telemetry instrument. Binsfeld Engineering.
Here we go fellas, to put this to bed once and for all??? This little baby if attached to your rear proshaft, between the IRD and VCU will tell you how much strain is on the shaft as a result of a gammy vcu. Any excessive force would obviously act on the IRD TO fook it. Now Im guessing as has already been mentioned so many times that this gizmo will set you back a good few quid. If you were LR independant or such however it could be a worthwhile investment to strap onto your freelander once or twice a year for a comparison of readings. Or we can purchase one as a club and all pass it around via special delivery :dizzy:

craigmidlands said:

No I just stumbled across this thread lol

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Aye, if you tinker in User CP, you can set 40 posts/page rather than eight/ten and switch signatures off...

My sig is quite annoying …

Don't see how this thing can measure torque

Rpm sure

But torque ?

Did we ever getanywherewith the mech vcu idea in the end? I'm sure it's doable with a selenoid and mini clutch type setup of one form or another

digby said:

Don't see how this thing can measure torque

Rpm sure

But torque ?

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We use very similar gizmos but on a much larger scale on large ships. Torque can be measured by a strain gauge set up fixed on shaft. Lasers may also be used to check distortion/ twisting of the shaft due to transmitted torque. Actually pretty straight forward, the more complicated part can be getting reliable readings to a receiver as obviously you can have wires connected to the shaft. Manys a night on the high seas we have slowed a vessel due to excessive propeller shaft torque. These things are common now and could prove useful in diagnosing transmission system faults.
I must point out that despite all of above im more in support of the good maintenance movement I.e., look after your freelander, service, use matching tyres, check wear regular and rotate. Know what symptoms are of tightening VCU and replace at recommended intervals.
Having said that im not having a dig at anyone who feels they would benfit more from some kind of reliable and accurate test for their peace of mind. The problems is doing it at a realistic price.

musky81 said:

The problems is doing it at a realistic price.

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Yeh, I googled that TorqueTrak 10K device - it sounds exactly what I was trying to describe above! Its referenced from loads of sites so is presumably a good piece of kit that does its job well. But, not 1 site I found listed a price - so you know its going to be bloody expensive!

It also looked a bit fragile and not the sort of thing you'd leave on the car all the time to warn of problems.

GrumpyGel said:

Yeh, I googled that TorqueTrak 10K device - it sounds exactly what I was trying to describe above! Its referenced from loads of sites so is presumably a good piece of kit that does its job well. But, not 1 site I found listed a price - so you know its going to be bloody expensive!

It also looked a bit fragile and not the sort of thing you'd leave on the car all the time to warn of problems.

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I thought exactly the same when I seen the price...must be a reason to keep it secret. It does definetly look the sort of thing that would be fitted for a health check and then removed again. Probably only any use in the hands of a place like bell engineering.

Spotted something on wheeler dealers t other day, which was the system an early Audi TT uses"haldex" wonder if these could be adapted to run from a switch or even as is?

Old thread I know not read it all so maybe mentioned..

"Haldex" is what F2 uses, and most 'AWD compact SUVs' that were released after about 2000 (I believe).

So surely (with the known fl1 vcu issues) it would make viable sense for someone/peeps that make haldex to make a retro fit kit, the key bit of kit exists so all it really needs is a mount and input / output shafts that will fit the current props UV splines?, and obv some wiring to a switch or a brain as the TT uses?

Obv its not going to be cheap cheap but ud guess most would buy one as and when required?