Another focus of the B7 RS 4 was on the introduction of the latest development of Audi's 'trademark' quattro permanent four-wheel drive system. This utilised the 'third generation' asymmetric/dynamic Torsen T-3 'automatic torque biasing' (ATB) centre differential, featuring a 'default' 40:60 front-to-rear torque split under normal conditions. Audi stressed that this would result in a more neutral response in corners and a more dynamic driving experience. Also, a more aggressive Torque Bias Ratio (TBR) was used, and set to 4:1, as opposed to 2:1 (and later variants 3:1 TBR) on standard A4. That means that one side of the differential can handle up to 80%, while the other side would have to only handle 20% of applied torque.