Page 246 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Fig. 8.1-75 Driven front axle of the Porsche 911 Carrera 4 (1996, 1998). The visco clutch is flange mounted directly on the front axle
to achieve a better distribution of axle load. With corresponding slip of the rear wheels, up to 40% of the driving torque is transmitted
to the front axles. Particular attention was paid during the adjustment of the four-wheel drive to predictable self-steering properties
independent of drive distribution and to controllability of the handling characteristics even at the stability limit. Instead of differential
locks, specific wheel brake engagements are made in order to retard spinning wheels. Four-wheel drive is integrated into the
Porsche Stability Management (PSM), a system for controlling the dynamics of vehicle movement with brake actuation.

Fig. 8.1-76 Double wishbone rear axle on the Audi A4 Quattro. The suspension subframe 1 is fixed to the body with four widely
spaced rubber mountings (items 2 and 3) and houses the differential casing 8 and transverse control arms (items 4 and 5). The
springs and shock absorbers are mounted next to the fixings for the upper control arms 7. The location 6 of the wheel hub carrier 5
was raised (long base c, Fig. 8.1-4) and drawn outwards. The lower transverse control arm 4 is fixed to part 1 with widely spaced
mountings. These measures ensure a wide boot and low forces, making it easier to attain the desired kinematic characteristics.