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 RS 4
The original B5 version was produced only as a five-door five-seat "Avant", Audi's name for an estate car/station wagon. The second version, the B7, was released initially as a four-door five-seat saloon/sedan, with the Avant following a short while later. A two-door four-seat Cabriolet version was subsequently added. Furthermore, their unique internal combustion engines are all front-mounted, and are longitudinally oriented. The transmission is mounted immediately at the rear of the engine in a longitudinal orientation, in the form of a transaxle, and contains both a center and front differential.