VC refills for Cancer Research UK

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Re: VC refills for Cancer Research UK

Postby bene » 28 Jun 2016, 18:02

Yep, that's the one...
Cheers dude.
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Re: VC refills for Cancer Research UK

Postby silverbullet » 28 Jun 2016, 21:17

No worries Dave

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Re: VC refills for Cancer Research UK

Postby silverbullet » 30 Aug 2016, 14:14

A little update. I have had a tip-off regarding some pioneering work being done in Austria on the VC front, whoever is behind it seems to have the their own unique testing machine so can verify any experimental work with a torque performance graph. If only I could offer the same :(

The long and short of it is that they are basically purging the VC with CO2 gas once filled, to mitigate the effect of the free oxygen in the VC airspace degrading the silicone fluid in service. I was sceptical at first, but their reasoning appears sound and following a back-to-back 10,000km test the results speak for themselves. http://vw-kern.at/index_en.php

I intend to start offering a similar improvement to the basic spec at no extra cost asap, its a small matter of using Argon/CO2 welding gas to displace the air before fitting the filling plugs. No fancy graphs, but working to the same formula as before and competetively priced, as ever :wink:

Of course this could bring a premature end to all my VC work by making them too reliable and long-lasting, but the seals will have to fail eventually!

Another detail that now seems to need addressing is the problem of VC body spline wear. This interface is poorly lubricated and the splines suffer from fretting (oxidization & dry wear) and this reminded me of the Land Rover LT77 transfer gear wear "fix", which was thought up outside the factory and then adopted some time after. These google images give some idea of the severity of the LR problem:
https://www.google.co.uk/search?q=LT77+ ... sfer+gear+

No need for us to put such a whacking great set of holes in the VC though :shock:

My proposal is to start drilling 3 x 1.8mm holes into the root of the splines on the VC body "spout", to help oil get in there and so arrest any further wear (3 are neccessary because there are 21 splines) They are so small as to have no material influence on the strength of the VC, but will give the gear oil a chance to lubricate the splines.

If you wish to assemble your VC with graphited anti-scuff compound as well, then so much the better...
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Re: VC refills for Cancer Research UK

Postby Winchweight » 30 Aug 2016, 16:29

Sounds interesting. I had seen the guys in Austria doing there thing via a page on FB.
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Re: VC refills for Cancer Research UK

Postby Aidan » 30 Aug 2016, 20:51

give me a spec or product for the graphite anti-scuff stuff and I'll use it in the workshop on reassembly

Interestingly the VCs I have seen recently have all been loads better on wear on the splines than the refurbished VCs we were seeing a few years ago which confirms in my mind that we were being sent the "pooh" cores after refurbishment by STEC and the Germans were cherry picking the best ones for themselves so I am so glad that Ian is refurbishing our VCs and keeping the good cores we have in circulation here.

Has Herr Hurlimann conributed to the purging discussion ?

You should receive 4 VC tomorrow
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Re: VC refills for Cancer Research UK

Postby silverbullet » 31 Aug 2016, 17:00

I have not been contacted by any of the known parties on the VC refurb scene.

I am of the opinion that any life-extension mods - such as improving the spline lubrication - are a good thing, especially in the case of the really good VC cores. Those that are badly worn are being retired to a box under the bench (nothing gets binned) but I have next to no good cores left, so please don't hoard them!

Any of these anti-scuff compounds would do the job, all are a high-Molybdenum/graphite content paste. https://www.google.co.uk/webhp?sourceid ... ff%20paste
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Re: VC refills for Cancer Research UK

Postby syncroandy » 31 Aug 2016, 18:00

Thanks for all this Ian.

This anti-scuff paste, do you think it'd be useful to apply this on the rear hub splines before assembly ?
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Re: VC refills for Cancer Research UK

Postby silverbullet » 01 Sep 2016, 10:27

There would be no harm in using it on the rear hub splines. By rights if they are torqued correctly then there should be no opportunity for the splines to experience fretting, but it gives some extra insurance e.g. in the event of bearing failure and the resultant loss of clamping force.

Re: VC casing spline condition assessment.

When looking at the internal form of the serrations, the crests and roots of the serrations should be near enough the same width, approximately 1.8 - 2.0mm

As the serrations wear on the driving flanks, the width of the crest at the inner diameter become narrower. This results in take-up "clonk" as power is applied by my reasoning.

PS Splines are typically coarse i.e. 6 up to 12 divisions around the circumference and parallel sided, as per rear hub shafts. Serrations are when you have significantly more, i.e. clutch shafts etc and with the "tooth" form cut at 60 or 90 degree included angle :wink:
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Re: VC refills for Cancer Research UK

Postby poshbuggers » 01 Sep 2016, 21:57

Mines feeling worn now. I'll be up for a rebuild soon.

PM me some information please :-)

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Re: VC refills for Cancer Research UK

Postby silverbullet » 02 Sep 2016, 13:00

Will do.

Some more things to check if you have a "spare" or are offered one (not sure if I have mentioned these points before, but a reminder doesn't hurt)

Looking at the cover end with the big circlip, in the bore of the hollow spindle you will see a pair of small holes near the open end. If they are full of black stringy debris then it has shredded a lip off the seal that end. There are two similar holes at the other end but a bit further in and the same applies.

While looking at the splines in the casing, take a look at where the spindle butts up against the end of the splines. It should be near enough flush and all neat and tidy down there. If there is a significant gap and the end of the splines are burred, it means that it has been abused (driven hard while the VC was slipping) and the spindle and casing may well have been making contact. We are talking about friction-welding conditions and it scraps both casing and spindle. I have several examples here.
If its not obvious, stand the VC clip uppermost and firmly but gently pus on the end of the spindle, if it drops significantly below flush* with the central boss on the end cap, it's damaged.

*Note: 0.5 to 1mm is normal

I have had a few VC where the casing has a "flare" toward the open end by the clip, where it should be parallel (the short bit before the angle)
It suggests that VC has been cycled way over the design pressure i.e flogged to death because it was tight and the temp/pressure inside has got so high that the end cover has tried to push the circlip out of it's groove (the thinnest part of the casing) so the metal has stretched. I won't re-use these at present, but may well have to start doing so if there is nothing else left and they are otherwise ok.

Finally the VC casing should be a nice bright steel, silvery and with a bit of blueing from the welds at the closed end. If your VC is blackened all over or looking like it's been baked or has a vintage gun-blued appearance, it's been badly overheated for any number of reasons.

Finally, there are early, late and end production variants but the parts are all basically interchangeable:

Early ones may well not have a date code (week/year) hand engraved on the narrow bit of the case diameter and have a full-house of internal splines* to drive the plates (50) and have shims to set the plate end-float. The end of the case has VW Audi logos, the word AUSTRIA, SDP initials and a GTW-S38 MTT part number cast in.

Late ones have a date code, five internal splines removed (makes for slightly faster filling/assembly, the fluid has somewhere to go) no shims and a 094 408 453 part number and SDP initials.

End of production units have an arbitrary 5-digit sequential part number (beginning 4, again hand-engraved) and the casing end has either:
"POZZI ITALIA" cast in along with the 094 part number or:
VW/Audi logos, POZZI SDP and the same 094 part number.

End covers are all the same: with VAG logos, AUSTRIA SDP and (a day/week casting date?) and 409457 MTT GTS-45

Just so you know :wink:

* I say splines, but they are more like an involute gear form)
Last edited by silverbullet on 13 Sep 2016, 09:38, edited 1 time in total.
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Re: VC refills for Cancer Research UK

Postby silverbullet » 06 Sep 2016, 16:06

Spline oiling holes have been test-drilled on a spoiled casing, so this will now be the default spec. I have yet to work out a means to easily purge the airspace with CO2/Ar gas but it's heavier than air so shouldn't be too hard, a simple funnel should do it.

I have had a few enquiries about doing these mods post-fill i.e. those VC that I have done but haven't got into vehicles yet. Not a problem, it's non-invasive and won't affect the calibration, but they will need to stand for a few days to make sure all the fluid has settled. I can do it for the cost of the shipping.

Allowing the fluid to settle and de-aerate is something that I have always done, it gets rid of the biggest bubbles that result from pouring and only takes a few minutes, so any free oxygen inside the casing will be minimal and should usefully extend the VC's service life.

Pic link later on!
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Re: VC refills for Cancer Research UK

Postby 69chop » 07 Sep 2016, 16:01

Hi there,
Having just come back from 1st camping trip in Devon, 5 hrs at a steady 55mph, petrol stops were full of scrubbing tyres, I think the VC needs sorting.
Just to be sure,
Drop the prop shaft out for now, to avoid any further wear ?
When time allows, drop the front diff, take out the VC, put back the diff, carry on driving without VC or prop shaft ?
Please PM me with details on how to book in VC rebuild.
Thanks,
Stefan
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Re: VC refills for Cancer Research UK

Postby silverbullet » 07 Sep 2016, 16:18

That sounds about the least painless way of tackling it. Get the prop removed asap.
I can turn your VC around within a week or so, maybe quicker if you are lucky, scarcely worth refitting the front diff unless its your sole vehicle. No booking in procedure as such, just phone and check that when you want to drop the VC in is OK this end. Richmond is close enough not to bother with couriers!

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Re: VC refills for Cancer Research UK

Postby 69chop » 07 Sep 2016, 20:39

silverbullet wrote:That sounds about the least painless way of tackling it. Get the prop removed asap.
I can turn your VC around within a week or so, maybe quicker if you are lucky, scarcely worth refitting the front diff unless its your sole vehicle. No booking in procedure as such, just phone and check that when you want to drop the VC in is OK this end. Richmond is close enough not to bother with couriers!

Ian


Hi Ian,
That's great, I'll call you before I drop it off to you.
Thanks,
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Re: VC refills for Cancer Research UK

Postby Campernutz » 04 Dec 2016, 05:32

First I've read this post as not been on in years! I may have some other spare VC units lying around for you Ian? :ok
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