The brief
The A3 had developed a chorus of noises while driving, a rattling, a clunking, and a growl that built up with speed. He brought it in worried, and the team tracked the main culprit down to a front wheel bearing. The wheel bearing lets the wheel spin freely on its hub while carrying the car's weight and the cornering loads. It's a sealed unit, and over the miles the bearing wears, the rollers and races pit, and it gets rough and noisy, the growl that rises with speed, and once it's badly worn it develops play, which adds a rattle and a clunk over bumps. A worn bearing only gets rougher, and a badly worn one can damage the hub and the brakes, so it needs replacing.
The diagnosis
On the lift the wheels got spun and rocked by hand. The bearing on the noisy front corner was rough turning and had play, exactly what makes that growl, rattle and clunk, while the others were tight. The noise tracked to that one corner, with the rest of the suspension checked over and sound. That's a bearing replacement on the affected front corner, it's a sealed unit, you don't repack it, so the call was a complete bearing or hub assembly as the design calls for, pressed and torqued to spec.
The work
The corner was stripped down, the worn wheel bearing pressed out, and a new genuine Audi-spec bearing fitted, everything cleaned up and reassembled with the hub nut and the suspension fasteners torqued to the manual figures. The wheel was refitted and spun to confirm it turned free and silent. A road test confirmed the growl, rattle and clunk were gone across the speed range and through corners both ways.
The outcome
A quiet, smooth-running front corner, no growl, no rattle, no clunk, whether straight or turning. The A3 went home with the bearing sorted. A worn wheel bearing only gets rougher and can take the hub and brakes with it if it's left, so changing it on the affected corner put it right before it became a bigger job.
