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 A6
There are now six petrol and four diesel engines available for the upgraded A6. All petrol engines now feature cylinder-direct Fuel Stratified Injection (FSI) technology, and all diesel engines now feature common rail (CR) and Turbocharged Direct Injection (TDI) technologies. There is a new petrol engine, a 3.0-litre supercharged V6, badged as 3.0 TFSI or 3.0T. This new engine is shared with the 2010 Audi S4 and S5 Cabriolet, although in the latter two applications in a higher state of tune and mated to a 7-speed S-tronic dual-clutch transmission.