'Channeling the engine's reserves to all four wheels is Audi's new rapid-shifting, seven-speed double-clutch gearbox and the latest version of its four-wheel-drive system, now featuring a nominal 40/60 apportioning of drive as well as a torque-vectoring planetary drive device at the rear. Referred to by Audi as an active-sport differential, it continuously varies the drive across the rear wheels to counter understeer and/or oversteer, taking less than 100 milliseconds to react, according to Audi.The new driveline brings about a major improvement in standing-start acceleration; the S4's claimed 0-to-62-mph time drops from 5.9 seconds to just 5.1 seconds in sedan guise, a time that places it just 0.2 second behind the former 420-hp, 4.2-liter V8-powered RS4.'