In 2000 Audi launched a new stepless transmission called multitronic. Based on the principles of continuously variable transmission (CVT) popularised by DAF, multitronic offers a stepless automatic transmission in which the ratio between the input shaft and output shaft can be varied continuously within a given range, providing a very large number of possible ratios. The multitronic system uses a chain drive, an oil cooled multiplate clutch (initially of six parts, later of seven to enable it to cope better with the torque of larger turbodiesel engines), and complex electronics, to overcome the traditional shortcomings of CVTs.
The transmission is monitored and regulated by Audi's "Dynamic Regulating Programme" (DRP), which tracks the driver's inputs, driving conditions, and engine load to compute the optimal gear ratio for fuel efficieny or maximum performance, as mandated by the user. The transmission can select pre-programmed underdrive to increase performance, or overdrive to improve economy. From 2004, multitronic gearboxes offered manual selection of a sport mode to pre-select the performance mapping. The electronic system also includes sensors to detect whether the vehicle is traveling downhill, and provides additional engine braking in such circumstances. multitronic also offers a number of driver-selectable fixed rations, selectable from either the gear-lever in a sequential style, or via (optional) fingertip paddle-shift controls. Early versions offered 6 ratios; in 2004, this was increased to 7. Some A6 variants that feature the multitronic gearbox are now equipped with the fingertip controls as standard. These controls can also switch to semi-automatic mode when one of the paddles is activated; however, they revert to fully automatic after a predetermined period of time.
multitronic offers performance and economy similar to, and in some cases better than, the equivalent six-speed manual gearboxes, and greatly superior to traditional geared automatic transmission. Particular performance advantages are noticed in 'in-gear' acceleration times over equivalent manual transmission cars.
multitronic is offered on front wheel drive versions of the Audi A4, Audi A5 and Audi A6. It is not compatible with the quattro (four-wheel drive system), or transverse engine in the Audi A3. At first the torque limit was 310Nm, but the gearbox is now modified to withstand 400Nm torque.
multitronic® is a registered trademark of AUDI AG.