Mechanism Of Viscous Coupling: Notes
The viscous coupling housing contains a number of inner and outer plates which are arranged alternately. The inner plate has its internal perimeter fitted to the external side gear (rear) splines while the outer plate has its external perimeter fitted to the internal center differential case splines. A spacer ring is provided to position the perimeter of the outer plate. The inner plate has no spacer ring and moves slightly between the adjacent outer plates, along the side gear (rear) splined in the axial direction.
A mixture of silicone oil and air is sealed in the space inside the center differential case. An "X" seal ring prevents silicone oil from entering the transmission. This could occur when silicone oil is highly pressurized due to an increase in rotating speed difference between the front and rear wheels.