DIY VCU service

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Hay jedi

What cst did you use in the end I have found the eBay seller again and he does loads of different viscositys I'm going to attempt my own refurbishment too so would like to get the bits I need
 
I used 30k cst...its quite loose compared to what it was. I did a one wheel up test and its a lot looserer....I can turn it quite quickly with my hand......but its got enough grunt to move the hippos own weight with me in it forward with just the rear wheels, so im happy with it....if I did another I would probably try a 60k cst...but then your going to get stiffer transmission wind up:eek:

The Hippo is mainly used for the shopping runs around town etc, so a loose vcu is what I wanted as it does a lot of 3 point turns, parking etc..

I suspect a stock vcu is nearer the 100k cst judging by how loose mine feels.

But again this all depends on how much of the old stuff you get out too....my baseline was a vcu I could quite easily turn with just my hands:)

Good luck bud:)
 
Cheers mate 60000 sounds perfect then for me as I want reliable offroad performance with less chassis ripping performance in reverse turns
 
Oh yes. ...you dont want any of that chassis ripping fluid....im amazed just how much stress a vcu puts on the transmission as compared to a proper diff....if I had that sort of resistance in a mechanical diff.....id be ripping the whole car apart to find out why?:eek:
 
I know I still can't get it in my head how it happens with a conventional rear diff anyway it behaves just like a locked rear diff and it's nasty
 
If you can turn your VCU by hand, then it may drive the rear wheels enough to push the car on smooth concrete, it may also give some better road handling characteristics and help in an icy supermarket carpark. These may be fine if that's all its going to do.

But I can't see it shifting the car on a wet car-boot grass carpark, any sort of incline and do nothing off road. I'm sure it would burn out pretty quick if it ever was tested in those conditions as well - if the TC didn't help the front wheels drive out of the situation.

Just my thoughts - and I'm no expert!

I'm in 2 minds about the VCU. There's plenty of people on here who think its crap. My brother, who builds LRs, says its crap. I at times have thought it crap. But at other times I think it actually does a pretty decent job and I'd rather change a VCU every 70K miles than a Haldex unit every 100K (don't know how reliable they are!).

What it needs is the ability to know when its 'in use' so you know it'll destroy the transmission if its 'on' when it shouldn't be! I'm also convinced that the majority of times a VCU has 'destroyed' the transmission is not because the VCU was broke, but because tyres were not right - once again and 'in use' signal would help.
 
GrumpyGel said:
If you can turn your VCU by hand, then it may drive the rear wheels enough to push the car on smooth concrete, it may also give some better road handling characteristics and help in an icy supermarket carpark. These may be fine if that's all its going to do.

But I can't see it shifting the car on a wet car-boot grass carpark, any sort of incline and do nothing off road. I'm sure it would burn out pretty quick if it ever was tested in those conditions as well - if the TC didn't help the front wheels drive out of the situation.

Just my thoughts - and I'm no expert!

I'm in 2 minds about the VCU. There's plenty of people on here who think its crap. My brother, who builds LRs, says its crap. I at times have thought it crap. But at other times I think it actually does a pretty decent job and I'd rather change a VCU every 70K miles than a Haldex unit every 100K (don't know how reliable they are!).

What it needs is the ability to know when its 'in use' so you know it'll destroy the transmission if its 'on' when it shouldn't be! I'm also convinced that the majority of times a VCU has 'destroyed' the transmission is not because the VCU was broke, but because tyres were not right - once again and 'in use' signal would help.
Click to expand...

The VCU is a good system, but only if you follow the strict tyre policy. A change at 70K miles is prudent too.
I'm not a fan of the Haldex unit. Whilst it's very clever, it's frighteningly expensive to fix when it goes wrong. The Haldex in the wife's VW Tiguan didn't even make 50K miles before it went bang!! Leaving her stranded in a soggy car boot field.
 
I like the vcu but I dont like the chassis ripping wind up this is its down fall:eek:...its basically on all the time...that resistance you feel on the one wheel up test is what your transmission has to cope with, when in reality with a mechanical diff or haldex you get zero resistance....

The vcu starts to lock up when turning the hippo round corners this is the same lock up as going up a muddy hill....

Even when driving in a straight line it still needs to slip...that extra resistance must have an impact on fuel economy? ...its like driving with the brakes on.:eek:

I prefer the haldex ive never know one to go bang thou? The pump motor can go on them . but other that that there pretty bomb proof...if they get too hot they switch off....I would say vcu for proper off road stuff thou.
 
jedi said:
I like the vcu but I dont like the chassis ripping wind up this is its down fall:eek:...its basically on all the time...
Click to expand...

The strain a correctly working VCU system puts on the drive train is minimal. Ten's of ftlb of torque. Don't forget, any torque "seen" by the VCU is divided by the diff ratio of around 3.8 iirc. So if you have to apply 80 ftlb of torque the turn the wheel, the VCU sees around 20 ftlb. 20 ftlb is nothing compared to the torque that is required to move a car down the road.

The problem isn't a strength issue, it's a maintenance issue. Or a lack of understanding on the peculiarities of the VCU drive train.



jedi said:
Even when driving in a straight line it still needs to slip...that extra resistance must have an impact on fuel economy? ...its like driving with the brakes on.:eek: .
Click to expand...

A correctly working VCU system causes almost no increase in fuel consumption. I measured 0.2 Mpg on my V6 over 5000 miles. Most of that saving is likely due to the reduced weight.



jedi said:
I prefer the haldex ive never know one to go bang thou? The pump motor can go on them . but other that that there pretty bomb proof...if they get too hot they switch off....I would say vcu for proper off road stuff thou.
Click to expand...

Maybe that's why LR chose the VCU in the Freelander?
 
The Haldex in the Yeti, a gen 4 one, needed oils changes every 40,000 miles. So roughly 2 oil changes compared to the VCU needing replacement. For the Yeti it was about £50-£60 for the dealer to do it, which you would pay if the car was under warranty.

I have heard of Haldex failures in the Yeti.

I sold mine before it needed any major work. That DSG gearbox is great, but very complicated and expensive to repair if it goes bang :D
 
So up to now I have fully understand how you can empty your vcu,how much is the exact amount of silicone , and what grade viscosity , you must put in in order to work correct? Sry for asking but I am a little confused with the amounts
 
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So after running my Re-furbished VCU over the winter months, I can gladly report back that all is ok, no leaks, funny noises etc, and best of all it hasnt exploded into a thousand pieces. :)

For road use and muddy fields the fluid used seems ok......and I get only the very slightest sensation of transmission wind up.. you really have to feel for it to notice it..

Which is great for my hippo as I no longer have to worry about the IRD, Rear Diff, and the Chassi ripping feeling.!!
 
Glad this thread popped up again as my VCU is lying forlornly in the garage waiting for the cash to replace it. Now I know how to fix it myself it is going to happen. :cool:
 
Having read through this thread, would a suitable DIY guide be:

1. Drill 10mm holes on opposite sides of the VCU 180deg apart.
2. Allow fluid to drain, helped by compressed air/solvent/heat.
3. Ensure VCU can be turned by hand.
4. Tap and plug bottom hole.
5. Refill with 60,000 cst siloxane - 160ml?
6. Tap and fit plug or grease nipple to top hole.
7. Test VCU on bench - ensure it turns slowly with breaker bar but resists rapid rotation. Adjust fluid volume as necessary.
8. With VCU fitted, do 1 wheel up test.
 
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