Date:         Fri, 6 Aug 1999 07:32:37 -0400
Reply-To:     Derek Drew <drew@INTERPORT.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Derek Drew <drew@INTERPORT.NET>
Subject:      New Information on Viscous Couplings
Content-Type: text/plain; charset="us-ascii"

The following is a repost of material sent to the Syncro List when the
Vanagon List was down. It contains important new information about the
Viscous Couplings. It belongs in the archives.
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ADDITIONAL INFO from the VERY BEST SOURCES:

1. If you refill a VC so that it is full it will burst its seals. Never
refill so it is full. (The proper percent air is 84% to 86% according to an
estimate from another expert familiar with Viscous Couplings but this
percent CANNOT BE CONFIRMED YET and the percentage is critical.) 290 Grams
of fluid is the SDP spec for the amount for a refill, but we need to find
out of 290 grams is actually the amount to put into the VC or simply the
order quantity.

1a. Someone should check with German Transaxle/Wheedle to see if they leave
the proper amount of air in the unit or not. There is now so much
corroboration (from both SDP and Visco Drive) that there needs to be air in
the VC that, no matter what they told me on the phone, it seems imposssible
that German Transaxle would be filling the VC so that it does not contain
air. I would imagine therefore that it was an error on my part to think
that they were not carefully assessing the proper percent air. But do not
have any repairs done with one of these outfits without at least confirming
this issue with them.

2. The plates inside the Viscous Couplings have microscopic burrs on them
that are critical to the proper torque transfer of these units. This means
that the plates wear out and should generally not be reused!!!!!!

3. Since replacement plates are not available, this means Viscous Couplings
rebuilds are questionable procedures and should be avoided.

4. Any viscous coupling under pressure is likely a bad viscous coupling! If
you open the unit, and a lot of VC juice comes out, the VC is likely bad or
going bad!!!!!

5. Viscous Couplings may be expected to last at least 60,000 to 90,000
miles. After that, they may become worn out and should then be
replaced!!!!!! This makes it sound like they should be replaced as often as
your clutch!!!!!

6. There is *no difference* between the Viscous Coupling fluid in the 14"
and 16" models.

The problem is that there are microscopic burrs on the metal plates. With
use, these burrs get worn down/off so they are suspended in the fluid but
they are important to imparting the proper torque. So the correct method
would be to order new plates at the same time as ordering new fluid and seals.

We do not have a source of plates and SDP gives us a cold shoulder when we
query after the plates or the fluid. But I would be interested to see if
the following part number yields them: 094 409 448 (or 44B cannot read
correctly).

We do not yet have a good source of the fluid but you can wheedle a can of
the fluid out of Wheedle for about $200. It would appear that you should
leave 14% air in the unit and that the correct fill amount is 290 grams of
the fluid. Tim says the fluid should cost more like $42. I do not really
trust that Wheedle is picking the correct fluid, so I would be cautious
about ordering it from them.

If the fluid in your old VC is of black color, this is said by Wheedle and
Oregon to be an indication that that fluid had gone bad. The fluid appears
to go bad after it absurbs a sufficient quantity of the microsopic burrs I
spoke of, so black fluid indicates the possibility you may wish to change
the plates as well.

There is a possibility that the following part number will yield from VW a
container of the correct fluid:

N 052 130 00

Can't be sure.

Most likely the part numbers I have provided must be ordered from a
European VW dealer because they do not show up in my USA microfiche.

After refilling and reinstalling everything, you will know you have done
the job right if your VC meets the following test:

Testing is being done by keeping the housing stationery and having the hub
rotate with a constant speed of 75 rpm. Temperatured is being measured by
means of a thermo coupling on the outside of the housing. Torque transfer
in Nm vs. temperature (C) at a speed difference of 75 rpm is the key
measurement. The torque level slowly *drops*! as the temperature goes from
10 degrees C to 120 degrees centegrade (from 250Nm to 140Nm) and then
shoots up to an infinite torque sharply at a point between a termperature
of 120C and 135C.

At 11:23 PM 8/4/99 -0400, you wrote:
>From: "karl" <thewestyman@mindspring.com>
>
>Today at my shop, I had my first run-in with the famed and often feared
>'Viscous coupling'. I was working on a Westy Syncro that I am getting ready
>to sell, and decided to test said coupling. Jacked the rear up, started it
>up, put it in gear, and........nothing! Not the slightest movement from the
>front. Well, I happened to be so lucky to have a 'spare' van here, so I
>pulled the front diff and transplanted it to the Westy. Works fine!
>
>Now for the 'fun' part. Having had a father who was a tinkerer (that's how I
>got my start in this business), I of couse had to pull the old diff apart to
>have a look at what troubled it. Wonderfully easy to remove the viscous
>coupling! On the bench, I removed the two small plugs from the side plate.
>Nothing ran out....hmmm.....it did have a somewhat foul odor though. Not
>knowing what to expect, I lightly placed the coupling in a vise, to hold it
>together as I removed the large snapring that holds it all together.
>Carefully loosened the vise, nothing popped apart. A couple taps with the
>plastic mallet, and the thing seperated. I have always been under the
>impression that these viscous coupling were some really complicated device,
>but it is not so. Basically, a cup-shaped housing, a side plate, a hub, and
>a stack of thin plates, alternating ones having holes or slots. Quite a
>simple assembly, IMO! This particular unit had very little fliud in it,
>however all the plates appear in very good condition, free of warpage. There
>was a small amount of fluid (more like sticky 'motor-honey') on the plates.
>The failure that allowed the fluid to escape was one of the seals on the
>hub. That's it--one little seal. This brings me to my next idea: if we can
>somehow get our hands on the fluid, as well as the two seals and one o-ring,
>we (or I) could rebuild these things at a very reasonable cost. Am I missing
>anything in my thoughts? Is there any reason, outside of finding the bits to
>'rebuild' them, that this is not a possibility? Please pardon me if I missed
>any pertinent postings recently, I guess I am guilty of using the delete key
>excessively. So, lets talk about this. Any thoughts?
>
>Karl Mullendore
>'87 West Syncro x 2 (1 FS)
>'87 Syncro 7-pass x 2 (both FS)
>
>
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_______________________________________________
Derek Drew                                            New York, NY
CEO, ConsumerSearch
drew@interport.net

212-580-6486
917-848-6425 (cell; this phone is a reliable way to reach me fast or to
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