Mine was doing the test in around 15 secs before I fixed the dodgy welding so I suspect it was loosing pressure hence the time. With this situation I noticed the front wheels slipping more on gravel than I would have expected so I suspect using 60k fluid would result in a similar result. Whether that will result in shorter or longer life of the new fluid is an interesting question.
BTW I also found the 1WU test took a lot longer when I had too much fluid in it, so quantity of fluid is as important as type.
 
I've got 400ml of 30K fluid for my VCU. Most of my driving is road based but I'm not expecting it to be totally useless off road. The only thing I'm expecting is there to be more front slip from the front before the rear starts to come into play.
If I find that there is to much front slip, I'll replace the fluid for 60K fluid instead.
 
Nodge68 said:
I've got 400ml of 30K fluid for my VCU. Most of my driving is road based but I'm not expecting it to be totally useless off road. The only thing I'm expecting is there to be more front slip from the front before the rear starts to come into play.
If I find that there is to much front slip, I'll replace the fluid for 60K fluid instead.
Click to expand...
You should have a word with @Joe_H about that - I think he'll suggest you've created a "chocolate frying pan" so far as any 4WD capability goes. He's just ditched a Portuguese VCU that I believe he thinks had 30K because it just did next to nothing.

It WILL be interesting though for you to find a wet grassy slope and give it some Go peddle from rest and see what happens. I would think that 30K viscosity isn't going to help much and you'll need to make sure you have a small enough air gap to lock the coupling - assuming it (the plate gaps) will lock with 30K.

If you do need to crank up the CST, at least it will be fresh and thin - so will flush easier!
 
I'd suggest you put in 150 grams and a grease nipple in the hole. That way you won't need to pull the VCU off to add more fluid if it is too loose (grease guns are cheap). There seems to be an optimal amount and if you go over that it starts to tighten up, so that might be easier than replacing the fluid.
I guess so long as the hole is near the outer edge you could also get the VCU to the position where the hole is at the top and use a big syringe to add more.
Edit:
I just remembered your not cutting your VCU open so maybe put in around 120g - 130g as there will always be stuff left in the VCU no matter how well you flush it out.
 
GrumpyGel said:
You should have a word with @Joe_H about that - I think he'll suggest you've created a "chocolate frying pan" so far as any 4WD capability goes. He's just ditched a Portuguese VCU that I believe he thinks had 30K because it just did next to nothing.

It WILL be interesting though for you to find a wet grassy slope and give it some Go peddle from rest and see what happens. I would think that 30K viscosity isn't going to help much and you'll need to make sure you have a small enough air gap to lock the coupling - assuming it (the plate gaps) will lock with 30K.

If you do need to crank up the CST, at least it will be fresh and thin - so will flush easier!
Click to expand...
I plan to experiment a bit regardless of who says what.
However I don't think I'll end up with no drive to the rear. I'm not planning on stripping the VCU. This means that a proportion of old fluid will remain in the unit. This old fluid will just get diluted down by the fresh 30K fluid. This will still provide me with plenty of torque to the rear diff.
Alibro said:
I'd suggest you put in 150 grams and a grease nipple in the hole. That way you won't need to pull the VCU off to add more fluid if it is too loose (grease guns are cheap). There seems to be an optimal amount and if you go over that it starts to tighten up, so that might be easier than replacing the fluid.
I guess so long as the hole is near the outer edge you could also get the VCU to the position where the hole is at the top and use a big syringe to add more.
Edit:
I just remembered your not cutting your VCU open so maybe put in around 120g - 130g as there will always be stuff left in the VCU no matter how well you flush it out.
Click to expand...
I have grease nipples and a grease gun to fill the unit with. I will play with levels and if it's too loose, I'll pump in a thicker fluid. It's not expensive and has a long life, so it's not a huge issue. I just need to develop an easy way to get new fluid in and old fluid out.
 
Nodge68 said:
I plan to experiment a bit regardless of who says what.
However I don't think I'll end up with no drive to the rear. I'm not planning on stripping the VCU. This means that a proportion of old fluid will remain in the unit. This old fluid will just get diluted down by the fresh 30K fluid. This will still provide me with plenty of torque to the rear diff.

I have grease nipples and a grease gun to fill the unit with. I will play with levels and if it's too loose, I'll pump in a thicker fluid. It's not expensive and has a long life, so it's not a huge issue. I just need to develop an easy way to get new fluid in and old fluid out.
Click to expand...
You will always be able to flush out the stuff at either end of the VCU and most of the stuff that collects down the slots but the fluid between the disks will probably never flush out.
I'd suggest a hole at either end directly opposite each other and some way to pump the fluid in under pressure.
 
Alibro said:
I'd suggest a hole at either end directly opposite each other and some way to pump the fluid in under pressure.
Click to expand...
That's the plan. I'll pump in the new fluid at the top of one end. Hopefully this will pump out the oil fluid from the other side bottom.
 
Nodge68 said:
This will still provide me with plenty of torque to the rear diff.
Click to expand...
I'm glad you know that. How do you know that?

I believe the Scandinavian crew have used 30K CST in "road cars" - but I don't think they expect any level of assistance off road - eg a grassey slope. They put in 60K or 100K (I forget which) for the cars they need any off road capability.

I am interested to see what results you get.
Alibro said:
I'd suggest you put in 150 grams and a grease nipple in the hole.
Click to expand...
Do grease nipples hold much pressure?

Have you used them @Alibro (or know of people that have used them)? I've seen people discuss using grease nipples but not sure if anyone has. It always strikes me that it will be very difficult to get ultra high viscosity fluid through a grease nipple.

The fill/drain/vent holes will need to be very close to the outside of the 'drum' to top-up with the unit still on the car. In some ways so long as you have access under the car, it is a good place to do it - cos it will be held firmly in place and won't rotate etc.
 
GrumpyGel said:
I'm glad you know that. How do you know that?

I believe the Scandinavian crew have used 30K CST in "road cars" - but I don't think they expect any level of assistance off road - eg a grassey slope. They put in 60K or 100K (I forget which) for the cars they need any off road capability.

I am interested to see what results you get.

Do grease nipples hold much pressure?

Have you used them @Alibro (or know of people that have used them)? I've seen people discuss using grease nipples but not sure if anyone has. It always strikes me that it will be very difficult to get ultra high viscosity fluid through a grease nipple.

The fill/drain/vent holes will need to be very close to the outside of the 'drum' to top-up with the unit still on the car. In some ways so long as you have access under the car, it is a good place to do it - cos it will be held firmly in place and won't rotate etc.
Click to expand...
I used grease nipples on the first VCU I did but never needed to use them so can't comment on squirting stuff in but haven't had any issues. Last one I just used bolts cut to length and will probably do the same with this one. Hoping to start it this weekend.
BTW I know it is a lot of hassle cutting it open and welding back together (or getting it welded) but I think it is the only way to do it properly and may even save a lot of time/hassle in the long run.
Edit Oh and be careful not to drill your hole too near the edge as the drum side wall is around 6-10mm thick with the splines. I'll measure tomorrow if I get it apart.
Check some of the photo's here. https://www.landyzone.co.uk/land-rover/looks-like-ive-done-it-again-doh.293904/
 
Last edited:
Nodge68 said:
Today I actually got time to test the VCU in my 05 TD4 SE auto. The vehicle has done 111K miles so I'm expecting to need to referbish it.
The time on the one wheel up test was 45 to 50 seconds with a 1.2 meter lever and 5Ks hung on the end.
So I don't think it's to bad just yet but I'll referbish it in the summer and give the results here.
Click to expand...

So what should the time be for a VCU in good condition.
 
From new they should be around 30 seconds, after a few years that will go up to a minute or so which is still OK (IMO). Once it gets nearer two minutes you really need to do something about it. Having said that my last one was nearer 3 minutes and the drive train was still OK but who knows for how much longer.
These are my opinions, others will disagree, but I feel these numbers are not too far away.
BTW as Joe_H found, the OWU test will only tell you if the VCU is unacceptably tight, it won't tell you if it will work well at putting drive to the rear wheels.
 
GrumpyGel said:
I'm glad you know that. How do you know that?

I believe the Scandinavian crew have used 30K CST in "road cars" - but I don't think they expect any level of assistance off road - eg a grassey slope. They put in 60K or 100K (I forget which) for the cars they need any off road capability.

I am interested to see what results you get.

Do grease nipples hold much pressure?

Have you used them @Alibro (or know of people that have used them)? I've seen people discuss using grease nipples but not sure if anyone has. It always strikes me that it will be very difficult to get ultra high viscosity fluid through a grease nipple.

The fill/drain/vent holes will need to be very close to the outside of the 'drum' to top-up with the unit still on the car. In some ways so long as you have access under the car, it is a good place to do it - cos it will be held firmly in place and won't rotate etc.
Click to expand...

I have used both 30.000 CST and 12.500 CST fluid and I really can't tell much differencde between them. What makes the difference I how much fluid you put in. You can make a unit solid it you pump it full with 12.500 CST and then you can drain a few cc at a time until it gets the friction you like. Grease nipples are great both for filling and draining. Just press the ball with a pen or a crosshead screwdriver and let the silicone seep out.
 
Last edited:
jonaf said:
I have used both 30.000 CST and 12.500 CST fluid and I really can't tell much differencde between them. What makes the difference I how much fluid you put in. You can make a unit solid it you pump it full with 12.500 CST and then you can drain a few cc at a time until it gets the friction you like. Grease nipples are greatcboth for filling and draining. Just press the ball with a pen or a crosshead screvdriver and let the silicone seep out.
Click to expand...
I agree that putting too much fluid in will make it extremely tight when testing by doing the OWU test but I'm not sure that using very low CST silicone and relying on extreem internal pressure of the VCU to control things is the correct way to go. The silicone supplier that sent me my fluid suggested 100k was correct for Freelanders and I suspect he is better placed then most to know. With advise from others and my own experience, approx 150g will give you a working VCU. I've tested it both with the OWU test and watching the rear wheels spinning on wet grass.
I'd be concerned that putting too much lower CST fluid would result in a VCU that feels correct when testing but ultimately slips too easily while driving.
 
I never weighed the fluid but if its density is something like 1.0 then 150 ml will make 150 grammes which I think is about the volume I used in the units I have done.
If they are to loose I just add a little fluid until they are OK for the use I want them to work with. Snow and ice in the winter and mud in the autumn hunting season require more grip than highway work during the summer. My experience is that once the correct amount of grip has been set it does not change with mileage.
 
Last edited:
jonaf said:
I never weighed the fluid but if its relative gravity is something like 1 then 150 ml will make 150 grammes which I think is about the volume I have used in the units I have made.
If they are to loose I just add a little fluid until they are OK for the use I want them to work with. Snow and ice in the winter and mud in the autumn hunting season require more grip than highway work during the summer. My experience is that once the correct amount of grip has been set it does not change with mileage.
Click to expand...
Cool, if it works don't knock it. :)
 
jonaf said:
I have used both 30.000 CST and 12.500 CST fluid and I really can't tell much differencde between them. What makes the difference I how much fluid you put in. You can make a unit solid it you pump it full with 12.500 CST and then you can drain a few cc at a time until it gets the friction you like. Grease nipples are great both for filling and draining. Just press the ball with a pen or a crosshead screwdriver and let the silicone seep out.
Click to expand...
jonaf said:
I never weighed the fluid but if its relative gravity is something like 1 then 150 ml will make 150 grammes which I think is about the volume I used in the units I have done.
If they are to loose I just add a little fluid until they are OK for the use I want them to work with. Snow and ice in the winter and mud in the autumn hunting season require more grip than highway work during the summer. My experience is that once the correct amount of grip has been set it does not change with mileage.
Click to expand...
These bloody Viscous Couplings!!

About the only thing that I thought was "definite" about them was that you need a very high 100K viscosity fluid - now you tell me, with evidence, even that is wrong!

These things are even more confusing than women.

How many years/KMs have the 12.500 CST VCUs been on the cars? Have you needed to change the fluid in them in that time? Will they still push a Freelander up a muddy/icy incline with loss of traction on the fronts?
 
When I did the one that is currently fitted to my car I had run out of 30.000 CST fluid. I had some 12.500 that I put in instead. This was two years ago and it has worked perfectly through two Norwegian winters with snow and ice. It works well in steep slippery inclines also.
 
Last edited:
jonaf said:
When I did the one that is currently fitted to my car I had run out of 30.000 CST fluid. I had some 12.500 that I put in instead. This was two years ago and it has worked perfectly through two Norwegian winters with snow and ice. It works well in steep slippery inclines also.
Click to expand...

I'm glad I bought 30,000 fluid now. If pressure affects the way the coupling works, then in theory the drive to the rear could be tailored to the season. More pressure in winter, less in summer. I can't see how that's really helpful, but it gives the option.
 
jonaf said:
I never weighed the fluid but if its density is something like 1.0 then 150 ml will make 150 grammes which I think is about the volume I used in the units I have done.
If they are to loose I just add a little fluid until they are OK for the use I want them to work with. Snow and ice in the winter and mud in the autumn hunting season require more grip than highway work during the summer. My experience is that once the correct amount of grip has been set it does not change with mileage.
Click to expand...
It just occurred last night, if I remember correctly you didn't cut the end off yours, so there would have been some residual stuff in still in the VCU before you put in the new fluid. That might account for the 150mls making it too tight.
I'm especially interested because yesterday I was standing with the grinder in my hand, about to cut the end off and had a change of mind. I'd done it that way three times before and really couldn't be arsed doing it again so instead drilled a couple of holes and left it overnight to drain. Yes guys I'm cheating this time. :p
I've drilled VCU's before and the previous ones drained very little, it's like the fluid in them had virtually solidified. The fluid in this one is much more viscous so I now have quite a puddle.
This is great news cause not only will it be much easier to flush out but it means the drive train will have had less strain on it. That is especially significant for my latest purchase as the propshaft was in the boot when I bought it. :eek: Normally I would have walked away but when I mentioned it to the dealer selling it he just pointed to the trashed support bearing and said he took it off because it was rattling. After checking if I could turn the VCU by hand with a couple of screwdrivers I went ahead and bought it. :confused:
 
Alibro said:
It just occurred last night, if I remember correctly you didn't cut the end off yours, so there would have been some residual stuff in still in the VCU before you put in the new fluid. That might account for the 150mls making it too tight.
I'm especially interested because yesterday I was standing with the grinder in my hand, about to cut the end off and had a change of mind. I'd done it that way three times before and really couldn't be arsed doing it again so instead drilled a couple of holes and left it overnight to drain. Yes guys I'm cheating this time. :p
I've drilled VCU's before and the previous ones drained very little, it's like the fluid in them had virtually solidified. The fluid in this one is much more viscous so I now have quite a puddle.
This is great news cause not only will it be much easier to flush out but it means the drive train will have had less strain on it. That is especially significant for my latest purchase as the propshaft was in the boot when I bought it. :eek: Normally I would have walked away but when I mentioned it to the dealer selling it he just pointed to the trashed support bearing and said he took it off because it was rattling. After checking if I could turn the VCU by hand with a couple of screwdrivers I went ahead and bought it. :confused:
Click to expand...
Presumably you meant to write "The fluid in this one is much LESS viscous".

Incidentlly, I'm sure this has been said before and I could find it searching through an umpteen page VCU thread, but what size holes do you drill and how far in from the edge of the VCU are the hole centers? Do you used "normal" drill bits, or a form of more 'flatter tipped' so as not to damage the plate on the inside of the case?
 
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