WARNING: FREELANDER SPARES VCU's

Chaser said:

under normal straight line driving with no front wheel slip the rear half of the prop turns faster than the front half. there's no argument about this, it's defined by the difference in front and rear ratio.

so the VC slips in two directions, the front only "drives" the rear half when there is front wheel slip and the speed of the front half of the prop exceeds that of the rear half.

until that front slip happens the rear wheels and rear prop are being rotated/dragged around by the motion of the vehicle, in other words the rear diff is in an overrun condition.

Click to expand...

nooooo! if either front or rear slips,then the diff in rotational speed of the two halves of the VCU will cause it to lock.

well refering to the 70/30 I read it somewhere and I will try to find where I read it will let you all know as anybody had a response of Freelander spares yet

As I understand it, a vcu in good nick does nothing until any wheels slip, then the viscous liquid heats up, stiffens, and causes the props to lock, giving all round drive. As long as the liquid doesn't heat up, i.e. the plates inside don't spin inside the vcu, stirring it up, then "2 wheel drive" is in effect. As has been mentioned, in theory a good idea, but as with most things of a liquid nature there is a sell by date, it will perish, the liquid will lose its properties. It would be beneficial to know what the liquids half life is, all things considered, although the recommendations for an 80k vcu change may be the way to go.

The Mad Hat Man said:

nooooo! if either front or rear slips,then the diff in rotational speed of the two halves of the VCU will cause it to lock.

Click to expand...

Yes i agree, but it doesn't do so (unless it's fooked) during normal on road driving, I was talking about normal driving with no wheel slip in response to those who think there is some magical division/split in drive torque under these conditions

one q for yu folks, if the VCU "works" by getting hot, what happens if yu get wheel slip when fording?

The Mad Hat Man said:

one q for yu folks, if the VCU "works" by getting hot, what happens if yu get wheel slip when fording?

Click to expand...

Hi MHM

I would imagine that it would operate no matter how cold, as it is a sealed unit, although in extreme cold it may take slightly longer to heat up and "shear" the liquid inside.

True, the fluid resists shear whatever its temperature and therefore is always capable of transmitting some drive even when cold.
As I understand it the friction generated by the molecules within the fluid increase temperature and resist shear at an increasing rate until it no longer slips. Fluid temperature probably increases far quicker than can be felt externally.

see the graphs ^^^^^^^^^^^^^^^^^^^^

Funny fred this.

When a Freelander travels in a straight line with no spinning wheels there IS drive to the rear wheels via the VCU. It’s difficult to define how much, but there IS some drive. Test as below:

On a Freelander left stationary enough to cool down jack up 1 rear wheel and turn it to take out the slack of the rear diff only. Now leave for 20 minutes to prove the VCU is at air temp. Now turn the rear wheel while watching the rear prop. After just a few degrees turn of the rear prop you’ll meet resistance. That resistance is across the VCU to the stationary front prop. A lot when turning yourself by hand, but little when compared to the drive force of your transmission.

I’ve filmed mine from cold on snow whilst pulling away fast. The VCU reacts quick. I’ll upload the video when I edit it to slow motion etc soon. Interesting results.

Be who cares? Test your VCU with the “one wheel up test” if you want to check it or think it may be at fault. Betterer still, buy a Freelander 2.

go and jack a wheel up and see if it slips easy ,and why did freelander have more issues than rr did ,rr had to wait till old age before v/c seized up so offered no differential

jamesmartin said:

go and jack a wheel up and see if it slips easy ,and why did freelander have more issues than rr did ,rr had to wait till old age before v/c seized up so offered no differential

Click to expand...

There's nothing wrong with my VCU. Not jacking up again. It works. Video below to prove it.

excuse my ignorance but out of interest do Freelander 2's have the same VCU set up?

no
i believe they have a "haldane" system

ah ok, thanks. Seems to have far more longevity from the sound of it.

"As before, drive is delivered mainly to the front wheels most of the time, but it can head rearwards when needed. Instead of a viscous coupling, though, the Freelander 2 uses a Haldane multi-plate clutch operated by hydraulic pressure"

from -> C! Magazine - The Ultimate Automotive Magazine

Hippo said:

There's nothing wrong with my VCU. Not jacking up again. It works. Video below to prove it.

Click to expand...

i bet its fine, you posted before me

It is a haldex system, I believe

crockett007 said:

It is a haldex system, I believe

Click to expand...

yup

http://www.awdwiki.com/images/nissan-x-trail.jpg

http://www.awdwiki.com/images/nissan-x-trail_x.jpg

tiz the X-trail, but similar system.

bugger

If there's always a slight speed difference between front and rear props surely there's always some sheer in the coupling, therefore more drive to the back than you might think? Maybe

Hippo said:

Funny fred this.

When a Freelander travels in a straight line with no spinning wheels there IS drive to the rear wheels via the VCU. It’s difficult to define how much, but there IS some drive. Test as below:

On a Freelander left stationary enough to cool down jack up 1 rear wheel and turn it to take out the slack of the rear diff only. Now leave for 20 minutes to prove the VCU is at air temp. Now turn the rear wheel while watching the rear prop. After just a few degrees turn of the rear prop you’ll meet resistance. That resistance is across the VCU to the stationary front prop. A lot when turning yourself by hand, but little when compared to the drive force of your transmission.

I’ve filmed mine from cold on snow whilst pulling away fast. The VCU reacts quick. I’ll upload the video when I edit it to slow motion etc soon. Interesting results.

Be who cares? Test your VCU with the “one wheel up test” if you want to check it or think it may be at fault. Betterer still, buy a Freelander 2.

Click to expand...

No hippo there isn't "drive", nothing from the engine is driving the rear diff. The bit you and others are missing is that because of the reduction at the IRD the front half of the prop is turning slower than the rear half. The rear wheels are in effect coasting and turning the rear diff and rear half of the prop.

The VC is slipping (backwards) because the front and rear road wheels obviously have to turn at the same speed.

That's why you can feel less drag when the VC is removed.

I don't know how else to explain it