Audi A6
Audi made a high-performance, 4.2-litre V8 engine (parts code prefix: 077, identification code: AEC) with a Bosch KE-Motronic ECU available as an option in the original European S4s, and made the decision to continue to do so with the S6, making a version of the 4.2 available as an optional upgrade over the 2.2-litre inline five-cylinder turbo. Unlike the five-cylinder turbocharged version, the V8-powered S6 was supplied with a four-speed automatic transmission as standard, but kept the quattro four wheel drive. A six-speed manual gearbox was also available as an option.
Torsen
The Torsen T-3 is currently employed as the centre differential in all non-Haldex Traction Audi models with a ZF-sourced automatic transmission Quattro four-wheel drive, such as: Audi A6, Audi A7, and Audi Q7. Audi uses a mechanical "Crown Wheel" centre differential for all longitudinal implementations using dual-clutch transmissions, such as the 2013/14 S4/RS4. Alfa Romeo used a Torsen C twin differential in the Alfa Romeo 156 Crosswagon Q4 and also in the 159, Alfa Romeo Brera and Spider Q4 models. Also, Toyota uses a Torsen T-3 in the center differential of the 4Runner Limited, FJ Cruiser 6-speed manual, Land Cruiser and Lexus GX470, with manual locking feature, and General Motors used a Torsen T-3 center differential in the transfer case of the Chevrolet TrailBlazer SS and Saab 9-7X (Aero model only).