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
In 2003 Volkswagen introduced the Direct-Shift Gearbox (DSG), a type of dual clutch transmission. It is an automated semi-automatic transmission, drivable like a conventional automatic transmission. Based on the gearbox found in the Group B S1, the system includes dual electrohydraulically controlled clutches instead of a torque converter. This is implemented in some VW Golfs, Audi A3, Audi A4 and TT models where DSG is called S-tronic.