Audi A4 allroad quattro – noise build-up during acceleration

In the vehicle type mentioned above, a distinct rattling or knocking noise may be heard coming from the front of the vehicle when the engine is running at low revs under load. The noise is particularly noticeable during acceleration in a higher gear, for example in 3rd gear, when on an incline. As the vehicle’s speed increases, so does the frequency of the noises.

If this fault is present and no abnormalities can be detected in the engine, gearbox, exhaust system or chassis during diagnosis, particular attention should be paid to the front drive shafts and also to the constant-velocity joints. Increased play in the inner or outer joint may cause speed-dependent knocking noises when under load. In vehicles with Quattro drive, high drive torques act on the front axle, which can lead to advanced wear on both sides.

The drive shafts must be checked for axial and radial play. In addition, the constant velocity joints must be checked for wear marks and for uneven movement when rotating. Noticeable stop points or a marked variable sluggishness when turning indicate wear in the joint. Leaky or torn joint boots lead to accelerated wear and tear of the joints resulting from loss of grease and the ingress of dirt. If any play or mechanical damage is detected, the affected drive shaft must be replaced in accordance with the manufacturer’s instructions.

Finally, a test drive is to be carried out under comparable load conditions in order to check whether the noises have stopped.