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 S5
Like all Audi "S" cars, they are only available as standard with Audi's quattro four-wheel drive (4WD) system, here in S5 using a Torsen-based centre diff system.