Vcu

The other thing that hasnt been mentioned is that VCU's can also fail by not locking up - Mondo had one like that. I like the idea of NI about checking rotational force (Torque) that would be the best way to check a VCU - if the torque required to turn it is between two known values - at least you know it wont be buggering up your IRD. maybe a machining mod so that the drive section is in two pieces with a drive pin to lock them together - when the VCU locks up the weakest point is the drive pin and that shears before the IRD gets trashed?
wots yo thoughts, NI?

howardo said:

£They don't explain why they think the tipp-ex test is a not a true test though.

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Tippex test isn't a test of the VCU's function. It will detect a SEIZED VCU but it won't detect a FAILED VCU.

The Ashcroft Test will do both.

Cheers

Blippie

The Mad Hat Man said:

The other thing that hasnt been mentioned is that VCU's can also fail by not locking up - Mondo had one like that. I like the idea of NI about checking rotational force (Torque) that would be the best way to check a VCU - if the torque required to turn it is between two known values - at least you know it wont be buggering up your IRD. maybe a machining mod so that the drive section is in two pieces with a drive pin to lock them together - when the VCU locks up the weakest point is the drive pin and that shears before the IRD gets trashed?
wots yo thoughts, NI?

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Who me?
You should know me by now MHM, I'm always up for a mod or two.

The torque values are not listed on the Bells site, is it a differential torque guage I wonder?
I see they offer a free test on the VCU, fine if the FL owners are local, bit hefty on the postage.

I was thinking of some sort of mod that a big fook orfe torque wrench could be attached to (1/2" drive)

Then the attachment could be 'shared' posted around the LZ members if they doubt the VCU performance......at the drawing board stage

yup - knowing the torque value wud be very useful - if difficult to check in situ. Once that was known it might be possible to determine the shear value required of a drive pin.

The Mad Hat Man said:

yup - knowing the torque value wud be very useful - if difficult to check in situ. Once that was known it might be possible to determine the shear value required of a drive pin.

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Thanks for all the input gang. Gazza has extensive experience of driving new FLs and i'm leaning towards a new (not recon) vcu. The problem is that we cannot drive each others motors so the level of the problem (up to complete failure) is impossible to guage. I am prepare to pay to improve the feel of mine and please wifey, whilst I accept that binding thing has become a normal feature of the mark. THis is the only thing I dont like about me FL so will shell out to cure. FL2 uses a Haldex clutch so presumably at least this problem has been engineered out. Cheers

Just a thought, would it be possible to replace the FL1 drive train (from ird to diff.) with FL2 drive train ?

its totally different. Not even sure the floorpan is similar.

Damn !!!!

ianda12 said:

Damn !!!!

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Sales manager at dealer told me FL2 in new from ground up - it does seem bigger but Ive not checked this. Doubt anything is compatable

DD3 - You don't seem content on what has been put forward.

The tightness on full lock is all part of the feel of 4wd, if you don't like the feel, change the motor, not the VCU.

As I have said before I have driven loads of brand new freelander and this fault was not detected by me in my own freelander when I notice it most is when I am pulling in to a parking space on full lock
It really slows down
My vcu has done 80k so it must need replacing when I turn on full lock and it feels as though the Brakes are on, what strain this is putting on the IRD

When I drove the freelander at gaydon I was always parking in tight spaces and never had this problem
If other people say that is normal for it to slow down on full lock ,may be very slight at first when new and not rely detectable ,but then progressively gets worse till your IRD fails under the strain

if the VCU is shagged - it will **** the IRD bigtime very quickly - go out and check yu VCU now!

The point is when does the vcu need changing
as mentioned before the vcu rarely seizes
so just because the vcu turns don’t mean to say its any good
all I am saying is a new vcu would turn easier than one thats done 80k miles
so my freelander thats done 80k miles will have more strain placed on the IRD
I am not happy thinking my IRD could fail at anytime
I have done the tippex test about 1 month ago and my marks have only moved about 1 inch
In a month so I could say my vcu is ok but its more likely to be Knackered

gazza666 said:

The point is when does the vcu need changing
as mentioned before the vcu rarely seizes
so just because the vcu turns don’t mean to say its any good
all I am saying is a new vcu would turn easier than one thats done 80k miles
so my freelander thats done 80k miles will have more strain placed on the IRD
I am not happy thinking my IRD could fail at anytime
I have done the tippex test about 1 month ago and my marks have only moved about 1 inch
In a month so I could say my vcu is ok but its more likely to be Knackered

Click to expand...

Well if you want piece of mind change it every 60k to 70k regardless of its apparent condition. Expensive though if its not really necessary.

How do you know it has only moved an inch ? It could have spun round dozens of times in a month (plus 1 inch ) when you checked it.
Also VCU do seize, usually after getting tighter over a period of time.
Another test is to jack the right hand rear wheel off the ground, leave the car in gear, put a socket on one of the wheel nuts with a long bar on it. Then lean hard on the bar and the wheel should very very slowly turn. ( This will also move the marks on your prop shaft.) If it doesn't turn your VCU is probably on the way out.

ianda12 said:

How do you know it has only moved an inch ? It could have spun round dozens of times in a month (plus 1 inch ) when you checked it.

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That's what I was thinking.

G13SJC sent me a copy of a transmission article from LRO magazine.

Their test was to drive on full lock, dip the clutch and FL should come to a halt slowly.
If it rolls back after stopping then VCU has seized.

Yes that sounds like a better test
If I drove on full lock then dipped the cluck mine would stop quite quickly
Don’t know whether it would roll back to suggest it is very tight
Will give it a go and see
So the vcu starts life pretty loose (not to lose) and progressively gets tighter and tighter
Till you IRD fails or you replace when you think it’s no good
The vcu is an expensive item to buy
So what we need is a way to be sure we are not buying one unnecessarily
Only buying one when we need to
So this test seems pretty good

When making tight turns on full lock increased power is required. Firstly the power steering pump is working much harder (and LR suggest that you dont keep it on full lock for any length of time because of heat generation). Secondly, if the VCU is working properly and not seized, it must slip since the net rear axle rotation is less than that of the front. This also dissipates energy due to the shear torque in the VCU fluid (thus warming it). Thus the engine is loaded more and will feel sluggish unless the throttle is increased. Indeed in the wheel jacking/rotation test it it stated that it should feel that the handbrake is applied, this is the increased torque that is required every time the VCU slips (and acts to reduce fuel consumption)

All of the mentioned tests will help to guage the condition of the vcu. But a worn vcu will not be as efficient as a new one. So if you are paranoid about strain being put on your ird you have no choice but to replace the vcu at 60k to 70k. I will not be replacing my vcu until it fails one of the mentioned tests.

So what are you saying?
A new vcu slips the same as on old vcu one that has done 80k miles till the point it seizes up
The point is we all know the vcu will slip and produce drag
But does that drag increase the more miles the vcu does probably yes
So at what point do we say the vcu as no good and putting extra strain on the IRD