Posting this for reference/discussion purposes. Later posts also document the taredown/rebuild of my own viscous coupler. While the Vanagon VCs are rebuildable, Syncro Passat VCs are not designed to be opened. To my knowledge this thread is the first example of a rebuilt Syncro Passat VC.
I thought about adding this to the FAQ but with the images and everything it could get to be pretty lengthy. There's really very little information about the Syncro viscous coupler out there, any time it comes up, someone just says something like, "It only locks when the front wheels slip" and dismisses any other information. While, yes, a properly functioning VC will lock when speed differential is different between front and rear wheels, there's really a bit more to it. Pay close to Section 5, it describes torque/power characteristics as functions of other variables such as silicone viscosity, internal pressure, and temperature. Important to note that if your VC seals are bad, the silicone inside (if any still exists) will fail to build pressure as it heats, and will perform poorly or not lock up at all.
I have also included a couple of links below with information on rebuilding the Viscous Coupler. I haven't had time to rebuild mine yet, but will most likely order a few seal kits and some silicone soon. If anyone here has experience with rebuilds PLEASE feel free to chime in. Thanks!
http://imageshack.us/a/img802/4387/vc1jpg.jpg
http://imageshack.us/a/img831/2532/vc2jpg.jpg
http://imageshack.us/a/img809/5108/vc3jpg.jpg
http://imageshack.us/a/img17/2705/vc4jpg.jpg
http://imageshack.us/a/img442/1338/vc5jpg.jpg
http://imageshack.us/a/img834/9273/vc6jpg.jpg
http://imageshack.us/a/img600/4917/vc7jpg.jpg
http://imageshack.us/a/img51/4535/vc8jpg.jpg
http://imageshack.us/a/img267/2511/vc9jpg.jpg
http://imageshack.us/a/img542/1816/vc10jpg.jpg
http://imageshack.us/a/img27/5987/vc11jpg.jpg
http://imageshack.us/a/img823/3169/vc12jpg.jpg
http://imageshack.us/a/img203/8748/vc13jpg.jpg
http://imageshack.us/a/img405/1486/vc14jpg.jpg
UPDATE - Here's the above set of images in a much handier PDF format. Page 8 is in tact as well: http://www.easy2design.de/stuff/visco_sae.pdf
I thought about adding this to the FAQ but with the images and everything it could get to be pretty lengthy. There's really very little information about the Syncro viscous coupler out there, any time it comes up, someone just says something like, "It only locks when the front wheels slip" and dismisses any other information. While, yes, a properly functioning VC will lock when speed differential is different between front and rear wheels, there's really a bit more to it. Pay close to Section 5, it describes torque/power characteristics as functions of other variables such as silicone viscosity, internal pressure, and temperature. Important to note that if your VC seals are bad, the silicone inside (if any still exists) will fail to build pressure as it heats, and will perform poorly or not lock up at all.
I have also included a couple of links below with information on rebuilding the Viscous Coupler. I haven't had time to rebuild mine yet, but will most likely order a few seal kits and some silicone soon. If anyone here has experience with rebuilds PLEASE feel free to chime in. Thanks!
http://imageshack.us/a/img802/4387/vc1jpg.jpg
http://imageshack.us/a/img831/2532/vc2jpg.jpg
http://imageshack.us/a/img809/5108/vc3jpg.jpg
http://imageshack.us/a/img17/2705/vc4jpg.jpg
http://imageshack.us/a/img442/1338/vc5jpg.jpg
http://imageshack.us/a/img834/9273/vc6jpg.jpg
http://imageshack.us/a/img600/4917/vc7jpg.jpg
http://imageshack.us/a/img51/4535/vc8jpg.jpg
http://imageshack.us/a/img267/2511/vc9jpg.jpg
http://imageshack.us/a/img542/1816/vc10jpg.jpg
http://imageshack.us/a/img27/5987/vc11jpg.jpg
http://imageshack.us/a/img823/3169/vc12jpg.jpg
http://imageshack.us/a/img203/8748/vc13jpg.jpg
http://imageshack.us/a/img405/1486/vc14jpg.jpg
UPDATE - Here's the above set of images in a much handier PDF format. Page 8 is in tact as well: http://www.easy2design.de/stuff/visco_sae.pdf