ASE A4 Suspension and SteeringSuspension System Diagnosis and RepairEasy
A customer complains of a low-frequency hum or drone that is audible from the front of the vehicle, particularly between 40-60 mph. The sound changes pitch slightly when turning left or right and does not typically change with engine RPM. Which of the following is the MOST likely cause?
- ADamaged constant velocity (CV) joint
- BWorn front wheel bearing
- CUnevenly worn tires
- DWorn inner tie rod ends
Show answer & explanationAnswer & explanation
Correct answer: B. Worn front wheel bearing
A humming or droning noise that changes with road speed and varies when turning is a classic symptom of a worn wheel bearing. The change in pitch during turns indicates that the load on the bearing is changing, which is characteristic of bearing wear.
Why the other options are wrong
- A. A damaged CV joint typically causes a clicking or popping noise, especially when turning at low speeds under acceleration, not a humming/droning noise at highway speeds.
- C. Unevenly worn tires can cause road noise or vibration, but typically a more consistent rumble or whine, and less likely to change pitch significantly with gentle turns.
- D. Worn inner tie rod ends typically cause clunking, loose steering, or wandering, not a humming noise.
Worn Wheel Bearing Noise
A characteristic humming, droning, or growling noise caused by degradation of the internal components of a wheel bearing, often due to lack of lubrication or wear.
- Noise increases with vehicle speed.
- Pitch/intensity changes when turning (loading/unloading bearing).
- Can lead to excessive wheel play if severely worn.
Memory trick: When the front 'HUMS', the 'BEARING' often 'DRONES' along.