All-Wheel Drive

1 – engine 2 – manual transmission 3 – front axle drive/differential 4 – drive shafts/front suspension 5 – propeller shaft 6 – Haldex clutch 7 – rear axle drive bevel gears 8 – rear axle differential 9 – drive shafts

CAUTION

Arrows indicate the direction of travel.

The all-wheel drive Audi A3 is equipped with permanent all-wheel drive. Driving the rear wheels additionally requires the following components:

A power take-off unit on the front axle manual transmission transmits drive to the propeller shaft, which connects the manual transmission to the rear differential. From the rear axle differential, drive is transmitted through the drive shafts to the rear wheels.

To accommodate the rear axle differential, the all-wheel drive Audi A3 has a double wishbone rear suspension and a two-part fuel tank.

To compensate for speed differences between the front and rear axles in all-wheel drive mode and to distribute torque between the front and rear axles depending on driving conditions, a Haldex clutch mounted on the rear axle differential is used.

The Haldex clutch is an electronically controlled, hydraulically actuated multi-plate clutch. Depending on signals from various sensors, such as the engine control module and ABS, the Haldex clutch control module regulates engagement of the rear axle. The all-wheel drive control system detects the cause of wheel slip and differences in wheel speed and distributes torque between the front and rear wheels accordingly. The rear axle can be fully disconnected from the drive, which removes towing restrictions with the front or rear axle raised. The all-wheel drive model can also be equipped with all electronic and hydraulic systems, such as ABS, EDS, ASR, EBV and ESP.

Towing all-wheel drive vehicles

All-wheel drive vehicles may be towed a distance of no more than 50 km at a speed of no more than 50 km/h. Otherwise, the vehicle must be transported on a special transporter with all wheels off the ground, fully loaded.

CAUTION

Do not start the engine when towing. General towing instructions are given in the Introduction.