Fig. 8.81. Transmission of the Passat SYNCRO car: 1 – differential of a forward axis; 2 – driveshaft; 3 – viskomufta; 4 – differential of a back axis

At all-wheel drive models the torque from the engine is transferred to all wheels. Operation of the automatic blocking device of intermediate differential is resulted by optimum distribution of engine capacity corresponding to a way of driving of the car and road conditions. In this regard all-wheel drive cars equally well behave at the movement on highways and highways both in normal conditions, and in adverse, and also in cross-country conditions. The torque from the engine is transmitted through the transmission and intermediate differential on differential of a forward axis, and from it — through the driveshaft — on differential of a back axis. At the movement on a dry covering the torque is evenly distributed on all wheels of a forward and back axis. If wheels on one of axes lose coupling with the road and will appear on the verge of slipping or pro-slipping, intermediate differential, without reducing torque size, automatically blocks wheels of this axis, transferring the big size of torque to the wheels of other axis having normal coupling with the road. Distribution of torque to wheels at all-wheel drive models uneven also depends on extent of coupling of forward or back wheels with the road. The differential of 4 (fig. 8.81) of the main reverse gear has the coupling of a free wheeling which disconnects the drive of back wheels when braking by the engine.

Reasons of the main malfunctions and ways of their elimination