The Audi R8 GT has the R tronic on board, which can be controlled via paddles on the steering wheel. The automated manual transmission offers the advantages of a manual gearbox – high efficiency, compact dimensions and low weight – but changes gears much faster than any driver could.
The speed at which the R tronic works varies as a function of engine speed and the shift program. Two manual and two fully automatic modes are available. At high load and revs, gear changes take only around one-tenth of a second.
The driver’s commands are transmitted electronically to the switching unit of the R tronic. Powered by an electric pump, its hydraulic fluid system provides the required pressure of 40 to 50 bar. The hydraulics actuate the clutch, which at only 215 millimeters (8.46 in) is very compact. This compactness is necessary because of the low installation position of the R8 engines. Gear changes are performed with the help of a second hydraulic block.
The R tronic also features the “Launch Control” program, which enables the R8 GT to spring into action in spectacular style. It modulates the throttle valves in conjunction with the engagement of the clutch at high startup revs so that the engine’s power is delivered to the road with minimal wheel slip.
With its longitudinally mounted mid-engine, the Audi R8 GT has a weight distribution of 43:57, and its quattro powertrain accordingly sends a majority of the power to the rear axle. The transmission is located behind the V10, and it includes an auxiliary drive for a prop shaft running below the engine to the front axle, where a viscous coupling distributes the power. In regular operation, it diverts roughly 15 percent of the torque to the front axle and can send up to an additional 15 percent to the front extremely quickly if the rear wheels begin to slip.
The primary component of the viscous coupling is a package of round clutch disks that rotate in a viscous liquid. If they rotate at greatly different speeds due to decreasing traction at the rear axle, the oil becomes more viscous as a result of its internal friction and increased torque is delivered to the front axle. A mechanically locking differential at the rear axle further improves traction. It provides up to 25 percent lockup when accelerating and up to 40 percent on the overrun.
The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.