Alternative to the fluid coupling (VCU)

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[QUOTE="Nodge68,. So if a spare tyre was used when a 300 Mile motorway journey is needed, added strain on the IRD could be avoided. I just think in those situations, it would be handy to disconnect the rear drive.[/QUOTE]

Well - without getting too extreme and overheating tires - a decent way of reducing IRD stress when obliged to use a mismatched spare might be to adjust tire pressures to achieve the right static rolling radius. (Normally the fronts run about 5mm smaller - hence the 0.2% gearing difference) This Idea occurred to me when I was playing with my propshaft revcounters - When I reduced the tire pressure in the rears till the rolling radius was the same front and back my propshaft revcounters picked up exactly the 0.2% gearing difference at the VCU. That was a very low pressure - about 20 if I remember - I only did a mile at lowish speeds to get the numbers.
 
I wonder what percentage of owners know Freelanders have an issue with the drive train? And what percentage of those who do, know it is caused by the VCU? From my experience most professionals in the car industry know nothing about it so I suspect the numbers of owners are very small.
 
Alibro said:
I wonder what percentage of owners know Freelanders have an issue with the drive train? And what percentage of those who do, know it is caused by the VCU? From my experience most professionals in the car industry know nothing about it so I suspect the numbers of owners are very small.
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If they stay within the operating instructions regarding tires etc - and take it to the main stealer regularly - they never need to know 'cos it will all work exceptionally well. Don't forget it's a world where most now struggle to open the bonnet and are totally scared off when they do - WE - the SPANNER brigade - are the dinosuars. -and we should know better than to fubar our trannys
 
dfossil said:
If they stay within the operating instructions regarding tires etc - and take it to the main stealer regularly - they never need to know 'cos it will all work exceptionally well. Don't forget it's a world where most now struggle to open the bonnet and are totally scared off when they do - WE - the SPANNER brigade - are the dinosuars. -and we should know better than to fubar our trannys
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That's a mighty big IF, especially since all FL1's are long since out of warranty.
 
Alibro said:
That's a mighty big IF, especially since all FL1's are long since out of warranty.
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Yeah -True - but you reap what you sow - People who run old machinery generally love old machinery and can get to grips with it's foibles - hence this forum - if they don't they go buy new - good job too - keeps us in work and generates a supply of old stuff for us in the future
 
Alibro said:
I wonder what percentage of owners know Freelanders have an issue with the drive train? And what percentage of those who do, know it is caused by the VCU? From my experience most professionals in the car industry know nothing about it so I suspect the numbers of owners are very small.
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I suspect it is very small in reality and many people who drive 2wd units are unaware as to the actual reason it became 2wd in the first place. There are also design 'faults' - or more correctly - areas that could be made far stronger that would help - for example - the support bearing for the rwd take off from the IRD. Many people suspect pinion bearings as an issue when it fact the failure of the crown wheel and pinion and subsequent severe damage caused mainly by the failure of the the crown wheel support bearing (the one closest to the crown wheel) This is the usual cause or an IRD catastrophic failure - this is almost always caused by vcu issues over time that a solid coupling cannot help but make worse. The second most common IRD failure is in area of the RH side inner CV support bearing (where the differential is) - this can be caused by the inner cv itself or the extreme load placed on the ird diff via the geared coupling to the layshaft / crown wheel area. This causes - in some cases - the diff shaft support bearings to partially collapse leading to failure of the large gear from the diff shaft to the layshaft. The thrust washers (the cup washers) in the diff in the IRD also can rapidly wear with the diff support bearing failing leading to major issues.
IMHO, a heck of a lot of these failures are caused by the vcu going into a premature hump mode under 'normal' driving conditions due to heat build up and fluid degradation over time - hump mode is the effective locked state and not a totally locked vcu (a very rare occurrence) in other words, the vcu will turn in a static test, but will rapidly lock (hump) - when out on the road (which is why I am personally not a fan of the OWUT - however I fully respect others opinions on the test!) Most of these failures are probably related to speed differential between front and rear caused by tyre state / sizing / mix etc leading to VCU failure over a prolonged period. There would also be a definite case for a VCU degradation occurring naturally over time -
Adding any form of fixed solid coupling will only exacerbate the issue. The VCU will allow a slight amount of slip in normal driving - however minimal and obviously - during cornering etc. A fixed solution will not - hence the build up of excessive load on the internal IRD / diff parts and also rear diff will eventually cause failure.
Running a decoupled 4WD system effectively 'ruins' the superb overall design of the freelander. Also - a fully working VCU will perform as well as a fixed coupling under conditions of wheel spin in a mild mannered and fully effective way without destroying the transmission or reducing the vehicle to a 2wd unit for most of the time losing all benefits of a beautifully progressive system

All the above is obviously IMHO.
 
Dont worry about the diameter differences using a spare tyre.

Remember that changing one tyre means that the differential on that axle will average out the difference in diameter between the spare and the old tyre on the other side, so the actual difference in propshaft speed between front and rear is half as much as it would be if you changed both tyres on one axle.

Example, if your spare is 10mm larger than the existing tyres and you get a flat on the rear, with the spare on, the rear diff averages out the difference between the left and right rears, giving an equivelant to a 5 mm difference between front and rear which is well within spec.
 
I'd think that very few owners of Freelanders appreciate what care needs to be taken (ie tyres/VCU).

Taking my own experience, I'd owned Land Rovers for many years before switching to Freelander. I had been told the tyres need to be "the same" and it has a viscous coupling that enables the A/4WD - but I didn't really appreciate what it all meant or how important these factors were. Truth is I didn't really think about it much, it was a car and as long as I don't do anything stupid with it and nothing breaks (like can happen with any car) then I'll be alright.

It was only when it went "bang" and I started investigating exactly how the uniqueness (I know its not necessarily unique) of Freelander's transmission works, that I understood why and how these things are important. Of course - that's almost always going to be "too late"!

I wouldn't think I'm to far different from 90% of Freelander drivers in that respect.

The silly thing is, (and this is probably where us LZ contributors are different to most of the 90%, or maybe its just me) its only since this happened that I've really got into and appreciate the Freelander - I think more of the Freelander now than I did when I didn't know much about it. Admittedly there were a few weeks when I hated the pile of c**p!
 
Were can I buy one and cost as I would try it it's ok knocking these things unless your willing to try how can you knock them, I'm willing to give it ago as I do a lot of rallies and towing a caravan across some of the fields sometimes the VCU don't kick in early enough,
 
Drdude said:
Were can I buy one and cost as I would try it it's ok knocking these things unless your willing to try how can you knock them, I'm willing to give it ago as I do a lot of rallies and towing a caravan across some of the fields sometimes the VCU don't kick in early enough,
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Hello there.
First off, can I congratulate you on a new record, 3 years 6 months for your first post:)
If you really want one, you'd be best off sending a PM to the OP @likimstip . It'll cost at least £1000. Possibly more.
But he seemed like a nice guy, and was happy to discuss the unit.

Good luck
Mike
 
Drdude said:
sometimes the VCU don't kick in early enough,
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Well its broke then - or a poor quality recon job. The VCUs should (essentially) lock-up the transmission within 1/8th, or at worst 1/4 of a front wheel spinning.

Get yourself a replacement new GKN unit or a Bell's recon. I think their respective prices are in the region of £370 and £250.
 
Can't be arsed to read it all!!!
A 2x4 - 4x4 locking system is asking for trouble. First time you forget to disengage it on Tarmac IRD goes bye bye cos of ratio difference front to rear. It still needs the vcu! So just fix the original system it works well and will be way cheaper.
 
Alibro said:
I wonder what percentage of owners know Freelanders have an issue with the drive train? .
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I'd say most at some time or another. It is buyers like I was recently that possibly are the ignorant majority. In all the FLs I looked at there was never an answer to the question "Has the VCU been changed?"
Thus is an old thread and I didn't read all of it but hey, it's an ongoing current issue. While sweating dealing with the VCU change I wondered why no one has ever cut a rear prop in half and engineered an electrically controlled mechanical freewheeling/lock system.
 
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