steely dan

steely dan

Active Member
Well after a couple of weeks in " Mondo " mode I'm going to go back to 4 wheel drive.
Drives very well in 2 WD but we have a long inclined gravel drive up to the house and the FL is digging in to the gravel all the time and churning it all up.
So, I will be fitting a new VCU and prop bearings.
Bearings I've sourced circa £30 in UK .
Over here in Ireland the VCU is approx € 800 ( £ 700 + ) so it's E bay for me . There are a couple of sellers on there selling the Oem part ( TOR 000010 ) at just sub £400 so due to the money involved my question is has anyone bought from any of them and if so were they reliable ? Their feedback is good but personal recommendations are better .
Alternativly, any suggestions as to a supplier at a similar cost ?

Cheers .
 
try ashcroft engineering or bell engineering.
bell do reconditioned ones for £200 with a 12 month warranty, you have to give them your old one though.
 
Can't offer an informed opinion on the VCs but regarding the bearings there have been many reports that the cheaper bearings are crap and don't last. Many have had to replace them again with OEM parts after as little as 12months use so I would go with OEM first off.
 
howardo said:
try ashcroft engineering or bell engineering.
bell do reconditioned ones for £200 with a 12 month warranty, you have to give them your old one though.
Click to expand...

Howardo .I've considered these but I cant understand how they replace the most important material in the VCU that is the silicone based viscous fluid. I always thought that this was the primary reason that the VCU " fails " ie the material steadily solidifies thus losing the slip .
If that is the case then it seems pointless fitting a recon unit even with a 12 month warranty especially at 2/3 the coast of a new one.
Whats the concencus of opinion here on them.
Chaser , Good point and I'll go that route ," do it once do it right "
Gegs 88 , Used Island a couple of times for brake discs and pads , Great service from them. I've e mailed them as they don't list it on their web site .
Thanks so far lads..
 
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theres a guy on here from bell engineering maybe he can tell us what they do.
If they take it apart maybe they can change the fluid in it, its just like silly putty apparently.
 
howardo said:
theres a guy on here from bell engineering maybe he can tell us what they do.
If they take it apart maybe they can change the fluid in it, its just like silly putty apparently.
Click to expand...

It would be of great interest to know what they actually do when they overhaul a VCU. The unit is welded-up, so it will have to be cut apart to get cleaned inside. I have tried to blow the gel out with compressed air after I removed the two steel ball plugs, without success. It is however possible to press fresh silicone into the unit with a grease gun, diluting the old gel. But as there also should be an amout of air in it this is the hard part.
 
It is however possible to press fresh silicone into the unit with a grease gun, diluting the old gel. But as there also should be an amout of air in it this is the hard part.

The fluid used in VCUs has a positive coefficient of viscosity, i.e its viscosity incresaes with temperatue. This is the mechanism by which the VCU operates. As the plates move relative to one another they shear the fluid , raising its temperature and viscosity so that more torque is required to further shear it. The shear torque transmits the drive. Because the amount of fluid between the plates is so small the temperature rises quickly,thus giving almost instantaneous drive.

Nornal silicone grease has a negative coefficient of viscosity, i.e it reduces as the temperature increases. Thus it should not be used in the VCU since under shear its viscoity will reduce and tranmit less drive. (Not exactly what is required unless you have a tight/seized VCU)
Ps. For the purist I realise that these fluids are non-Newtonian
 
if yu :search: this has been covered ad-nauseam for at least 4 years! It is NOT Silicone, it is a Silicone type medium with ickle balls in it. the best answer for a VCU is to bin it and replace it with an electrical Dog Clutch. Also discussed in detail. Some guy in Oz (Taz i think) was building one.
 
vic.middleton said:
It is however possible to press fresh silicone into the unit with a grease gun, diluting the old gel. But as there also should be an amout of air in it this is the hard part.

The fluid used in VCUs has a positive coefficient of viscosity, i.e its viscosity incresaes with temperatue. This is the mechanism by which the VCU operates. As the plates move relative to one another they shear the fluid , raising its temperature and viscosity so that more torque is required to further shear it. The shear torque transmits the drive. Because the amount of fluid between the plates is so small the temperature rises quickly,thus giving almost instantaneous drive.

Nornal silicone grease has a negative coefficient of viscosity, i.e it reduces as the temperature increases. Thus it should not be used in the VCU since under shear its viscoity will reduce and tranmit less drive. (Not exactly what is required unless you have a tight/seized VCU)
Ps. For the purist I realise that these fluids are non-Newtonian
Click to expand...

I have tried to heat the VCU to 60 deg C and also cool it to minus 15 (left it outdoor for a couple of hours - right now it's 20 below, brrrr) but could tell no difference in twisting force.
I think the temperature dependent silicone is the stuff that is used i cooling fan clutches and not in VCUs.
 
the vcu does get hotter when its been used. I don't think external temperature affects it operation.
 
jonaf said:
I have tried to heat the VCU to 60 deg C and also cool it to minus 15 (left it outdoor for a couple of hours - right now it's 20 below, brrrr) but could tell no difference in twisting force.
I think the temperature dependent silicone is the stuff that is used i cooling fan clutches and not in VCUs.
Click to expand...

Agreed jonaf, VCs use a shear thickening fluid, nothing to do with temperature change....
 
So , what about these "loose " VCU's Fully rebuilt with thinner gel .Anybody know about them ?
Bear in mind our FL sees no off road action at all.
 
Got a reply from Island 4X4 re recon VCU's . None in stock and won't be until end of March. They also insist on it being an exchange sale which has a cost effect to me.
I spoke to David Beaumont Gearboxes ,
David Beaumont 4x4 Gearbox Specialists
who offer a recon unit ( no exchange from ROI ) filled with a lighter grade Gel which is termed " loose " . I asked the advantages of these and they said it caused less stress on the drivetrain but suggested that an original spec item would be better if serious off roading or caravan towing was required. Ours is never off road or used to tow.
They also said that the tightening effect on lock was noticable less due to the different slippage rate.
Anyone know of these VCU's or have any experience of them ?
 
Sorry to hijack this thread, but just how tight on full lock is considered normal? Mine was tight enough so that it would'nt roll backwards on a gentle gradient. Straighten the front wheels and away it would go!! I replaced VCU with a recon, and it really does'nt seem any different? Feels like the brakes are binding!!
Cheers,
Russ
 
For what its worth...
I replaced mine with a Bell Engineering Recon in Oct 2008, for 200 quid.
done 25000 since then, no probs..(fingers crossed)

I went and collected/swapped mine over.
and chatted to the chap there, i think he said his Son either worked for or had worked for LR and had tracked down the supplier of the gunk in question.
so that was how it was sourced.

as to how its applied, dunno.

I'm happy with mine, so far..
 
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