Subaru 2002 Impreza Service Manual page 273

CENTER DIFFERENTIAL
Manual Transmission and Differential
C: FUNCTION
When there is no speed difference between the front and rear wheels, the center differential deliv-
ers the engine torque to the front and rear wheels at a ratio of 5050.
When a rotating speed difference occurs between the front and rear wheels, the center differential
operates to absorb it in a controlled way by the function of the viscous coupling.
1. DURING NORMAL DRIVING
During straight-line driving on aflat 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 drive axles. The
viscous coupling does not generate shear torque because there is no relative movements be-
tween the inner and outer plates.
(B)
NF0123
(1)
Engine torque (A) To front differential (B) To rear differential
2. DURING TURNS AT LOW SPEEDS
During turns at low speeds, rotating speed difference occurs between the front and rear wheels,
as well as between the left and right wheels. More particularly, the front wheels rotate faster than
the rear wheels. The center differential then acts to absorb the speed difference to enable smooth
driving.
Although the speed difference is small under this condition, operation of the viscous coupling
causes more torque to be transmitted to the rear than to the front.
NFO124
MT-13