The A3 Sedan will initially be fitted with one of two transmissions. The 2.0 TDI will be paired with a six-speed manual transmission, while a seven-speed S tronic is standard with the TFSI engines. As in all Audi transmissions, the gear spread is large. The lower gears have relatively short gear ratios, while the highest gear is comparatively long to reduce engine revs on long rural drives. Short gearshift travel makes it easy to precisely shift the six-speed transmission, which excels thanks to its high efficiency ratio.
The seven-speed S tronic combines the convenience of a classic automatic transmission with the dynamics and efficiency of a manual transmission. It namely comprises two sub-transmissions, which are actuated by two multi-plate clutches. The large K1 clutch located on the outside directs the torque via a solid shaft to the gear wheels for gears 1, 3, 5 and 7. A hollow shaft rotates about the solid shaft. This hollow shaft acts on the gear wheels for gears 2, 4 and 6 as well as reverse. It is connected to the smaller K2 clutch, which is inside the K1 clutch.
Though only one subsidiary transmission is engaged with the engine at any given time, both are continuously active. For example, when the driver accelerates in third gear, the fourth gear is already engaged in the second sub-transmission. Shifts are performed by switching the clutches. This takes just a few hundredths of a second and happens without any noticeable interruption in propulsive power.
The seven-speed S tronic is just 37 cm (14.57 in) in length and weighs some 70 kg (154.32 lb). The two clutch mechanisms do not require an oil supply, which further boosts their already impressive efficiency. A regulated electric oil pump supplies the clutch and gear actuators.
Revs are somewhat higher in the automatic S mode, whereas D mode prioritizes taller gear ratios. When combined with the Audi drive select dynamics system (standard in Ambition), the S tronic includes a free-wheeling function in efficiency mode that further reduces fuel consumption. The driver can control the seven-speed S tronic via the selector lever. Audi can install optional shift paddles on the steering wheel.
Outstanding traction: quattro permanent all-wheel drive
Audi will initially offer the A3 Sedan with front-wheel drive. Down the road, the quattro permanent all-wheel drive system will be paired with the more robust engines. It features a newly developed multi-plate clutch that is hydraulic and electronically controlled.
In the interest of better axle-load distribution, the clutch is located on the end of the prop shaft and in front of the rear-axle differential. Inside is a package of plates that rotate in an oil bath. The metal friction rings are arranged behind one another in pairs. One ring of each pair is rigidly meshed with the clutch basket, which rotates with the prop shaft; the other ring is meshed with the output shaft to the rear-axle differential.
During normal driving, the clutch sends most of the engine’s power to the front wheels. If the front axle loses grip, the clutch can steplessly redistribute torque to the rear axle within milliseconds. A piston automatically presses together the plate packages. The requisite oil pressure, generated by an electrically actuated axial piston pump, can reach nearly 400 bar. A pressure accumulator is no longer needed. Moreover, the clutch has shrunk and is 1.4 kg (3.09 lb) lighter than its predecessor.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.