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 A4
The next A4, internally designated "Typ" 8E, debuted on 10 October 2000, now riding on the Volkswagen Group B6 (PL46) platform. The car's new styling was developed under Peter Schreyer between 1996–1998, inspired by the Bauhaus design language of the C5 (second-generation) Audi A6 introduced in 1997. The 1.6-litre base model powerplant remained unchanged, but most other petrol/gasoline engines received either displacement increases, or power upgrades. The 1.8-litre 20-valve Turbo was now available in two additional versions, with or , this one with a standard six-speed manual gearbox, while the naturally aspirated 1.6-litre inline-four engine and 2.8-litre V6 were replaced by 2.0-litre, and all-aluminium alloy 3.0-litre units, still with five valves per cylinder, the most powerful of which was capable of and of torque. The 1.9 Turbocharged Direct Injection (TDI) engine was upgraded to , with Pumpe Düse (Unit Injector) (PD) technology, and was now available with quattro permanent four-wheel drive, while the 2.5 V6 TDI high-end model was introduced with and standard quattro. This generation of quattro consisted of default of 50:50 front to rear dynamic torque distribution. A Bosch ESP 5.7 Electronic Stability Programme (ESP) system, with anti-lock braking system (ABS), brake assist, and electronic brakeforce distribution (EBD) were standard across the range.