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.
Multitronic
Early versions offered six ratios; in 2004, this was increased to seven, while new Audi models now have Multitronic transmission with eight ratios. Some Audi A6 variants that feature the Multitronic transmission are now equipped with the fingertip controls as standard. These controls can also switch to semi-automatic mode when one of the paddles is activated; however, they revert to fully automatic after a predetermined period of time of inactivity.