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
Audi announced the B9 S4 in 2015, with the official unveiling of the European-spec model at the 2015 Frankfurt Motor Show. Noticeable changes to the B9 included a modernised, more angular exterior, newly designed wheels, and a new turbocharged V6 engine. Unlike the pre-facelift B8 S4, the announced European-spec model is only available with an 8-speed torque converter automatic (ZF 8HP55a).