Viscous Coupling judder

tonyt37 · Mar 16, 2009

Noticed a juddering on the VCU when cornering tightly. I checked to see if its seized by jacking up a back wheel and turning with the wheel brace. The wheel turns with moderate pressure but goes at different rates (easier / harder / easier) as it rotates.

Is it knackered?

vic.middleton · Mar 16, 2009

When cornering tightly the rear axle rotates slower than the front so the difference is 'lost' in the VCU. (Oh for a real differential!).
If you were on loose ground one explanation could be that a wheel was slipping and you were feeling the effect through the transmission.
If you were on solid ground a reason for the stick/slip behaviour is misalignment of the plates in the VCU caused by either swash in the plates or worn bearings. Although the VCU is suppoesed to be a 'sealed for death' component I have seen threads of members refilling/rebuilding them.

Chaser · Mar 17, 2009

tonyt37 said:
Noticed a juddering on the VCU when cornering tightly. I checked to see if its seized by jacking up a back wheel and turning with the wheel brace. The wheel turns with moderate pressure but goes at different rates (easier / harder / easier) as it rotates.

Is it knackered?

I'd say it was. The normal feel when rotating one wheel is pretty tight (takes all my strength) but should be smooth.

freelance · Mar 20, 2009

but the more you turn the wheel the harder it tries to stop you, this is normal, and means it is actually working correctly, you would do well to mark front and rear propshafts and check for non alignment of your marks on a regular basis.,usually they work or they are seized there is no in between,

The Mad Hat Man · Mar 20, 2009

freelance said:
but the more you turn the wheel the harder it tries to stop you, this is normal, and means it is actually working correctly, you would do well to mark front and rear propshafts and check for non alignment of your marks on a regular basis.,usually they work or they are seized there is no in between,

Rubbish - thay can fail so that there is no drive thru the VCU as well.

freelance · Mar 20, 2009

woops, my knuckles are stinging, but i imagine its 80.20 ratio seized against freedom on hippo

Dann · Mar 20, 2009

tonyt37 said:
Noticed a juddering on the VCU when cornering tightly. I checked to see if its seized by jacking up a back wheel and turning with the wheel brace. The wheel turns with moderate pressure but goes at different rates (easier / harder / easier) as it rotates.

Is it knackered?

Possibly. The system is sadly flawed and as Vic M points out really needs a proper centre diff or selectable 4WD. You don't say how long you've been driving a flander as they do have a tendency to drag themselves round tight corners on dry tarmac in an alarming manner. I personally run ours without props from April to October to reduce wear/tear/tyre wear and fuel consumption. Your VCU is either normal or siezed so mark front and rear props with tippex and check after a few journeys if the marks are still aligned then it (VCU) is siezed.D..

tonyt37 · Mar 24, 2009

Thanks for that guys. It is definately not seized but not smooth in operation either!
Dann how does it drive with the prop off? I was thinking of taking it off at least until I was sure about VCU. Can't afford that and IRD!

radian · Mar 25, 2009

How is your rear tyre wear? If its seized you will get a kind of wave in the wear of the tyre also scuffing when on full lock in a car park style slow turn.

Check the mounts they can split.

also if its not a v6 check the weight is firmly stuck all round as they can come off too and cause vibration.

ianda12 · Mar 25, 2009

Search 'mondo mode'

tonyt37 · May 23, 2009

Went Mondo last week as I was going on a 600 mile round trip. What a difference to fuel consumption! Seems a bit lite on the front though and not used to wheel spin when pulling out of junctions. I will see how it goes for now and might put it back before winter.

vic.middleton · May 23, 2009

Surprised that you can get wheelspin on a Freelander! The VCU must be doing its job.
Have you checked the rubber mounts of the VCU bearings? If they are shot it would allow the unit to whirl giving you the vibration. Easy to give them a good looking at now you have them off.
Yes the VCU does increase fuel consumption since it is increasing the torque going down the prop shaft and dissipating energy as viscous friction and ultimately heat.

Viscous Coupling judder

tonyt37

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vic.middleton

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Chaser

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freelance

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The Mad Hat Man

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freelance

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Dann

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tonyt37

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radian

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ianda12

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tonyt37

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vic.middleton

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