Date: Thu, 5 Aug 1999 00:44:07 EDT
Reply-To: Modl6971@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Modl <Modl6971@AOL.COM>
Subject: Attention syncro owners,
tech info on trans & VC's from German Transaxle.
Content-Type: text/plain; charset="ISO-8859-1"
Just thought that you guys showed see what German Transaxle in OR. states in
their paperwork that comes with your new transmission and VC. The paper work
has been scanned, so there may be a few spelling mistakes. See ya, Michael
87 syncro
87 quattro
What you should know about Vanagon Syncro viscous couplings (and why we have
a limited warranty on them. and why you may not want to install one):
We have had a fair number of viscous couplings and/or front differentials
returned to us as ‘locked up’; every one of these units tested just fine on
our bench. And upon inspection the coupling had no defect whatsoever The
Vanagon viscous coupling is a very simple device for transmitting power to
the front wheels of the vehicle. Basically, it consists of a shaft from the
driveshaft going Into the coupling, and a shaft going out of the coupling to
the front differential. There is no direct mechanici coupling between the two
shafts. The only connection between input and output is via a very thick
(viscous) silicone fluid; you could call it an almost zero-slip torque
converter. The job of the viscous coupling is to allow a very small amount of
slippage between the front and rear wheels (for going around turns), while
giving full power to the front wheels should the rear wheels start to slip In
snow or mud.
Viscous couplings ‘fail’ when they overheat and lock up solid, no longer
allowing any slippage at all. When this happens the van binds up and does not
want to move in even the slightest of turns.
There are two situations which cause churning or overheating of the viscous
coupling:
1. Driving the vehicle with anything but 4 absolutely identical tires. If all
tires do not have the exact same rolling circumference, the front and rear
axles will be turning at different speeds. This will cause the coupling to
churn, cook itself and can cause damage to the entire drivetrain.
2. Having ANY misalignment, either up/down or left/right, of the
engine/driveshaft/front diff. Huh? Here’s the deal: if the
engine/driveshaftlfront diff are not in an absolutely straight line with one
another, the driveshaft will be slightly speeding up and then slowing down
with every revolution. This causes a churning within the viscous coupling,
which will immediately bind up the unit.
THEORETICALLY, THE VISCOUS COUPLING SHOULD NEVER GO BAD, IF EVERYTHING ELSE
IN THE VAN IS OK IF YOUR CUSTOMERS HAS GONE BAD, SOMETHING HAS CAUSED THIS TO
HAPPEN. THERE IS EVERY REASON TO BELIEVE THAT THE
SAME THING WILL HAPPEN TO OUR UNIT! ARE YOU SURE YOU WANT TO GET INTO THIS
BAG OF WORMS?
When your customers car left the factory, you can be sure that the drivetrain
was perfectly aligned In every plane. Since then, how many times has the
engine been out? How about the driveshaft? Front duff moved around to change
front CV joints’ Any of these activities can cause misalignment of the
drivetrain, which will cause the viscous coupling to churn and lock up. If
your customer complains of binding, we suggest this quick test: with trans in
neutral, engine off, jack up the right front wheel. Put a socket on one of
the wheel lugs, and about a 2-foot breaker bar on the socket. You should
verrrrry slowly be able to turn the wheel, with great difficulty. Wont turn
at all? Let the van sit overnight, and try it again in the morning, stone
cold. If you can turn it when cold, there is nothing wrong with the coupling;
something is causing the coupling to churn when driving, locking up the
coupling.
Since we have no control whatsoever over the condition of the vehicle in
which our viscous coupling and/or front differential is installed, we cannot
cover installation costs for front differentials/viscous couplings replaced
under warranty if we get our unit back and find no problem with it. Happy
trails...
The difference between U-joints (which the drlveshaft has) and cv (constant
velocity) joints, Is just what the name Implies. The more expensive CV joints
tum at constant speed regardless of angle, while U-joints speed up and slow
down with every revolution, unless they are absolutely lined up wIih whatever
they’re tumlng. Prove it to yourself with a sir universal Joint and a couple
of extensions.
German Transaxle of America, me
Service/Warranty Bulletin: VW Vanaaon Svncro 4WD
It has been brought to our attention that transaxle failure in 4WD Vanagons c
happen simply by having different sized tires being fitted to the front and
re wheels of the vehicle. Here’s why: the Syncro van normally drives the rear
wheel there is, however, a driveshaft coming out of the front of the
transaxle, going the front of the van, where it attaches to a ‘viscous
coupling’, which is in turn attached to the front differential which drives
the front wheels. The visco coupling is a simple clutchlike device which
locks up solid if there is a differen in speed between its input and output
shafts. When the vehicle is underway, the re wheels normally drive the car,
with almost no power being transmitted through t viscous coupling to the
front differential, because front and rear wheels are ho turning at the same
speed. However, should the rear wheels start to turn a different
speed from the fronts (slipping in snow, ice, etc.),i$~e viscous coupli
instantaneously locks up, sending power to the front wheels. It stays locked
as long as there is tension on it (that is, as long as front and rear are
trying to turn different speeds). As soon as full traction is regained, all
wheels are turning at same speed, and bingo, the viscous coupling relaxes;
once again, power is going the rear wheels.
You can observe the functioning of the viscous coupling Like this: find an
empty parking lot, get the Vanagon going about 20 mph, and slip it into
neutral. Then coast normally. Now turn the steering wheel to the right or
left, and crank
farther and farther. You’ll feel the van bind up, slow down, and quickly come
to
complete stop if you turn the wheel far enough. This is because in a sharp
turn the front wheels of any car turn a different speed from the rears. In
the Syncro Van thus causes the viscous coupling to lock up and try to get
both front and rear wheels turn the same speed, but it can’t, because you’re
on pavement. The whole drivetrain is now in a bind, fighting against itself,
which brings the van to a stop.
*
If you’ve been following this, you’ll now realize why you can’t have different
tires on the front and rear of the Syncro Vanagon: THE VISCOUS COUPLING WILL
LOCKED UP CONSTANTLY, TRYING TO GET BOTH FRONT AND REAR WHEELS TO TURN AT THE
SAME
SPEED. TIRES OF DIFFERENT CIRCUMFERENCE OBVIOUSLY CANNOT TURN AT THE SAME
SPEED,
AN ENORMOUS STRAIN IS CONTINUALLY BEING PUT ON THE ENTIRE DRIVETRAIN
SPEEDS. THE TRANSAXLE WILL GROSSLY OVERHEAT AND BE DESTROYED.
IT IS ABSOLUTELY NECESSARY THAT YOU CHECK THE CUSTOMER’S CAR TO~SEE THAT IT
HAS
IDENTICAL TIRES. NOT JUST THE SAME SIZE. BUT THE SAME MANUFACTURER AND TREAD
DEPTH
FAILURE TO DO SO WILL CAUSE DESTRUCTION OF THE FRONT DIFFERENTIAL AND/OR
TRANSAXLE DUE TO OVERHEATING! WE WILL NOT REPAIR UNDER WARRANTY TRANSAXLES
WHICH
HAVE BEEN OVERHEATED. OUCH! IT IS CRITICALLY IMPORTANT. (AND POTENTIALY
EXPENSIVE) NOT TO INSTALL OUR TRANSAtLE UNLESS THE VEHICLE HAS
IDENTICAL TIRES.
Volkswagen doesn’t mention this possible problem in their owner’s manual (u,
please give this sheet to the customer. If you have any questions, please
call us
Thanks!
We strongly recommend the use of Redline MT’ 90 synthetic gear oil in all
Vanagc transaxles. They will shift easier and last Longer.
:
42fl
Name of selling Dealec Otoolln’s B.il.vue VW
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