Rear-wheel drive automatically
The automatically engaging all-wheel drive makes possible the easy operation, without an additional differential locking. It
engages without the intervention of the driver and, It can be developed with relatively low construction effort from the two-wheel drive.
In the case of a transverse mounted engine, an additional bevel gear drive, with a gear ratio differing from one, is installed in the final drive (figure 2). In addition a visco-clutch is required near the front- or the rear axle.
It provides torque to the rear axle when traction is lacking on the front axle. Other than the gear ratio between the crown- and the pinion gear, the drive train to the rear axle does not differ from that used in a
front engined car with rear-wheel drive. Here, the gear ratio is, in comparison to the front, reverse arrangement of the two bevel
If one takes a very good look, one will also notice that the rotation direction of the cardan shaft differs from that of the standard
drive. Also the viscous coupling in the diagram is located close to the front axle and in all other images integrated rear. The arrow in figure 2 indicates the point from where the cardan shaft transports the torque to the rear, if