Solid Shaft
From VanagonWiki
Tom Lengyl designed and makes the solid shaft. It is sold by most of the Vanagon/Transporter parts vendors in the U.S.
A solid shaft replaces your viscous coupling and removes the so called "intelligent AWD" provided by the viscous coupling. A solid shaft must be used in combination with a decoupler and the driver must choose when he wants to have his van in 4WD mode, or not.
So why would you want to remove the viscous coupling?
The solid shaft is usually preferred by Syncro owners who spend a lot of time offroading. It provides better off road performance in some conditions, like sand, mud, or loose gravel and dirt. The solid shaft eliminates the initial spin of the front wheels that occurs just before the viscous coupling locks up and converts your Syncro to AWD. It is thought that this inital spin, although possibly less than a full wheel revolution, is just enough to cause the tires to break traction, bog down and the van to get stuck. With a solid shaft, there is no spin before lock up. Power goes to all four wheels instantly.
I installed a solid shaft a year ago and immediately noticed improved performance while climbing steep hills with loose gravel and dirt at Syncro de Mayo. This performance comes with a compromise, however. You no longer have full time AWD or 4WD. You cannot leave your van in 4WD mode on paved roads. It will cause a lot of tire scrubbing when turning and premature tire wear. Tom Lengyl has reported that he drove his van all the way from his home in Oregon to Syncro de Mayo at Hollister, CA, without any damage to his tranny or other drivetrain components. A solid shaft will probably not be preferred by someone who owns a Syncro primarily for its AWD performance in snow and ice....conditions where the viscous coupling excels.
IMHO you have to be a dedicated "wheeler" (off roader) to want to use a solid shaft.
If you want one, it is a fairly easy DIY job to install. It's the same process as replacing the viscous coupling...only you put in the solid shaft instead of the VC...It slides right in (Warren Chapman)
