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 R8
The transmission options are either a Lamborghini-sourced six-speed manual gearbox with metal gate for the shift lever, or an Audi-developed "R Tronic" gearbox—which is a semi-automatic, without a traditional clutch pedal with automatic gears shifting mode.