Mechanism Of Viscous Coupling: Torque
When a difference in rotating speed between the center differential case and the side gear (rear) occurs, a viscous shearing force is generated in the silicone oil placed between the outer and inner plates. The torque is then transmitted by the silicone oil between the center differential case and the side gear (rear).
The greater the difference in rotating speed between the center differential case and the side gear (rear), the greater the shearing force of the silicone oil. The relationship between the torque transmission and rotation speed difference is shown in the figure. As can be seen from the figure, the smaller the rotating speed difference, the lesser the torque transmission and the differential-action.