A noise that follows the car's speed
A rumbling or whining that rises as the car accelerates and fades as it slows down comes from a component that rotates with the wheels: the secondary shaft or differential bearings, the gearbox output gear set, or a wheel bearing. The key challenge is telling the gearbox apart from the running gear.
The likely causes
- Secondary shaft or differential bearings. The noise changes depending on the gear selected, or between acceleration and lifting off the throttle.
- Wheel bearing. The noise is unaffected by gear selection but changes noticeably when cornering, as the weight transfers onto the wheel.
- Worn gear set on one ratio. The whining only appears in one particular gear.
| Test | If the noise… | It most likely comes from |
|---|---|---|
| Change gear at the same speed | changes or disappears | The gearbox |
| Take a wide corner | increases on one side | A wheel bearing |
| Coast in neutral | persists without changing | The running gear or differential |
Can you keep driving?
Yes, in the short term, as long as the noise remains a gentle hum. A bearing that overheats or seizes can, however, lock a wheel or damage the gear set: a noise that worsens quickly, turns metallic, or is accompanied by vibrations calls for immediate inspection.
Repair or replace?
A wheel bearing can be replaced without touching the gearbox. If the noise is coming from inside the gearbox, the job involves removal and strip-down: on a high-mileage gearbox, a reconditioned exchange gearbox, with new bearings and wear parts, warranted for up to 24 months, is often a safer option than a partial repair.
