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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