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 A4
The Audi A4 B5 saw nearly constant minor changes and alterations throughout its seven-year run. Moreover, a significant facelift was introduced for the 1998 B5 model year at the 1997 Frankfurt Motor Show, with sales beginning in Europe in early 1998. The 2.8-litre 30-valve V6 engine replaced the 2.8-litre 12-valve. A 2.5-litre V6 Turbocharged Direct Injection (TDI) diesel engine with was standard on the quattro. A six-speed manual gearbox was available, as well as the new high-performance Audi S4, now part of the A4 lineup (the previous S4 had been an Audi 100). Cosmetic updates included new rear lights, headlights, door handles, and other minor exterior/interior changes.