Continued... All three engine versions come standard with a new, eight-speed tiptronic electronically controlled with quattro permanent all-wheel drive. A dynamic sport differential is available as an option (standard with the 4.2 TDI quattro).

The eight-speed tiptronic is a torque converter transmission with a high overall gear ratio of 7.0:1 between the shortest and longest gear ratio. It rolls along the highway with low, consumption-reducing engine speeds in the two highest gears. It also allows to perform a kickdown by shifting directly from the eighth gear into the fourth.

Audi says that compared to the six-speed tiptronic of the previous model, the new transmission reduces fuel consumption by roughly 6 percent, requires less space for installation and has fewer distinct individual parts. Like in other Audi models, the differential is installed in front of the torque converter. This shifts the front axle far forward, bringing the advantages of a long wheelbase and a better weight distribution.

The newly developed, hydraulically damped centre differential is made of ultra lightweight magnesium with the V8 TDI and aluminium with the other two engines. The front of the tiptronic and also the engine are connected to the front axle frame by means of two hydraulic bearings.

Once the engine has heated enough cooling water, a valve in the loop opens and the hot water flows on to the transmission oil heater, which reduces the friction losses due to cold oil.

The torque converter lockup clutch is closed during normal driving, connecting the transmission directly to the engine. It works with limited slip in certain situations, which in conjunction with the damper precisely tuned to the engine permits very low engine speeds without vibrations.

When the A8 comes to a stop, an internal clutch separates the transmission from the engine, even if D is still selected. The torque converter therefore is not working against a stationary turbine which is more efficient with respect to energy. The clutch reengages as soon as the driver releases the brakes.

Slightly different variants of the eight-speed tiptronic are available depending on the engine. When used with the 3.0 TDI, it also includes a small, permanently full hydraulic accumulator on board to ensure start-stop functionality. When first started, the oil that it contains – roughly 100 millilitres – is forced into the actuating elements required for startup by a spring tensioned piston. The transmission is operational within a short time, much faster would be possible without the accumulator.