Date: Mon, 12 Jan 2004 22:43:51 -0500
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: VC Confusion
In-Reply-To: <BAY13-F1145DYge2Qw400063fe5@hotmail.com>
Content-Type: text/plain; charset=us-ascii
The VC is really engaged anytime the van is moving. The concept of
engaging or disengaging is misleading. No matter how well you match
tires, drive straight, etc., all 4 wheels will spin at slightly
different speeds. The crown in the road or simply going side to side
makes this so. If the connection between the front and rear wheels was
solid, these differences would be taken up as a combination of tire
scrubbing and excessive mechanical wear. Under normal conditions, the VC
allows these differences to be absorbed. This is accomplished by
allowing the shafts on each side to turn individually. The beauty of the
VC is that it can do this without the use of friction plates that would
wear or need regular adjustment. Think of the VC as a glorified limited
slip differential. There is always some torque being applied to the
front wheels. Now, for the so called engagement part, if the difference
in shaft speeds is great enough, than the plates shearing the magic
fluid will cause the viscosity to increase, thus increasing the torque
transferred and apparently locking up the front axle. This happens
quickly. In fact, if you removed a rear axle shaft, you would still be
able to drive the van using the VC and the front wheels and you will
hardly notice the difference. When making sharp turns, this effect is
what causes the van to feel like things are binding.
As for life of the VC, all the ones I have seen fail have one thing in
common, abuse!. Off roading and miss matched tires are the leading
causes of VC death. If you are getting stuck, and the rear tires are
spinning and the front tires can't pull you out, ten guess, what! You
are cooking the VC. If the VC becomes overly aggressive, then the fluid
at some point was overheated. If the plates wore so that they no longer
transfer torque or the fluid leaked out, then you have excessive age or
mi matched tires did it in.
If you have no signs of VC trouble, then do not worry about it. Jack up
one front wheel, if it is difficult to turn then it is connected. If it
turns with liitle resistance, then there is no torque transfer to the
front. If it is difficult to turn the van while driving or you keeping
breaking CV joint bolts or the tires squel on turns, then the VC is
cooked and should be replaced. BTW, the FUN BUS is now at 212K with the
original VC and it still goes in snow.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Jason Willenbrock
Sent: Monday, January 12, 2004 8:01 PM
To: vanagon@GERRY.VANAGON.COM
Subject: VC Confusion
hey all,
i was reading Derek Drew's Brilliant article about Syncro's VC on the
Syncro.org website. This is a very informative article and website!
One thing that confused me however, was a statement about the life
expectancy of the VC. According to the Article it states, the VC should
last 60,000-70,000 miles. My confusion is this, does that mean
60,000-70,000 miles period or while the VC is engaged? Without really
knowing everytime the VC is engaged how can this be measured? My Syncro
Westy has roughly 60,000-70,000 miles on it and no sign of VC problems,
however, i believe the UJoints are starting to go. So should i start
saving for a new VC now or do you figure the VC has only been engaged
1/3 of those miles so maybe only 25,000 miles on he actual VC? Any
insight here would be great
TIA
Jason
87 Syncro westy Project
90gl
87 Wolfsburg
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