Audi S4
Audi's quattro four-wheel-drive system was standard on the C4 S4/S6; a first-generation Torsen-based system which used the "T-1" automatically biasing centre differential (ATB) was used on vehicles equipped with manual transmissions, while a transfer box based system was used on vehicles equipped with an automatic transmission.
Audi S4
There were two different types of high performance brake systems on offer for the C4 S4. All S4s' initially had diameter by thick, radially ventilated disc brakes up front, each with an ATE single-piston sliding caliper inside a 'UFO' styled bell-shaped disc. With the introduction of the V8 engine, a new front brake setup became standard; again the discs used radial ventilation, but these front discs were now sized at by - with a conventionally mounted Lucas-Girling caliper in an external position over the disc. US models had smaller discs. The rear brakes, by and also radially ventilated - remained the same throughout C4 production; they used a Lucas-Girling single-piston sliding caliper with an integrated cable-actuated handbrake mechanism. A Bosch three-channel operation (four-channel sensing) Anti-lock Braking System (ABS) with a mechanical load sensing valve for the rear brakes was standard throughout production.