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 Quattro
At the Paris Motor Show in 2010, Audi presented the quattro concept on the occasion of the 30th anniversary of the original Audi Quattro and the Audi quattro four-wheel-drive system. Based on the RS5, it features a modified 2.5 L five-cylinder TFSI engine shared with the TT and a 6-speed manual transmission from the S4. The engine was claimed to generate a maximum power output of and of torque. The revolutionary design features depicted on the concept car would eventually make their way on future Audi models.