Description of a VC. it is somewhat like a clutch type device. it has a center spline which goes straight to the Rear driveshaft, and an outer spline which is connected to a chain which goes over to the front driveshaft. well in between these splines is a puddy type fluid, which when speeds on the inner and outter splines changes dramatically (rear wheels spinning faster then front- slipping detected), the fluid hardens and causes a bond for the inner and outter spline making them spin at the same speed (locking them together).