During Normal Driving
WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2014 Subaru XV Crosstrek, 2014 Subaru Impreza WRX, 2014 Subaru Impreza, 2013 Subaru XV Crosstrek, and 2013 Subaru Impreza. However, it is still accessible from the selected car via links, so may be relevant.
During straight-line driving on a flat road at a constant speed, all the four wheels rotate at the same speed. The center differential delivers engine torque evenly to the front and rear wheels. The viscous coupling does not generate shear torque because there is no relative movements between the inner and outer plates.