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
In Europe, the wide range of Audi A4 saloon and Avant estate are available with the 1.8 TFSI, 2.0 TFSI gasoline engine, as well as 2.0 TDI, 2.0 TDIe, and 3.0 TDI diesel motor. Trim levels are Attraction, Ambition, and Ambiente. In the UK, the A4 range is offered in SE, SE Technik, S line, and Black Edition model grades. All wheel drive quattro are offered in most engine and grade combinations.