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
For 2002, Audi increased power in the 1.8 Turbo engines to and – the 190 PS variant designated by a red 'T' on the boot lid. Available with four wheel drive and in the 2.5 TDI intermediate version to . A 2.0 engine with Fuel Stratified Injection (FSI) was also available. A year later, Audi reintroduced the S4, now powered by a 4.2 L V8 engine, as well as an A4 Cabriolet convertible variant ("Typ" 8H), finally replacing the 80-based Audi Cabriolet which had been discontinued in 2000. It included an electro-hydraulic operated roof, which lowered in under 30 seconds and incorporated some styling changes, such as body-coloured lower bumper and sill panels, which later found their way to the saloon version.