Whirring/slight grinding noise on acceleration at high speed

Question

Car is a Mk1 Golf with manual 5 speed and 1.8lt engine.

When travelling at above 60kph and accelerating or cruising I've noticed a slight whirring, or grinding noise. It almost sounds like a tyre is rubbing against something, thought I am very certain this is not the case (new suspension, tie rod ends and recent wheel alignment).

The sound stops when decelerating and is not heard at low speeds or at idle.

Clutch and gear shifting feels fine, though there are worn linkage bushes.

Could this be wheel bearings? Or gearbox bearings?

Answer 1

If it's a wheel bearing you can first try jacking the car up and grabbing each front wheel from side to side and then top to bottom feeling for any excess 'play'. Also.. assuming this is a standard gearbox (no limited slip or locking differential etc) you can try... CAREFULLY & SAFELY jacking up each front wheel 'separately' and have someone drive the car in second/third gear with each wheel off the ground, listen to each hub/bearing for a rumble. ALWAYS be prepared to hit the brake!

You can also 'CAREFULLY'.. on a straight wide road, try SLIGHTLY weaving from side to side to load each wheel bearing. If it is a wheel bearing the hum/rumble usually increases as each bearing is stressed.

If the sound is continuous above 60kph and doesn't change tone when you press the clutch or change gear then it's possible that the gearbox mainshaft.. or more likely the differential bearings could be the issue. If the tone does change when you change gear and accelerate then input shaft bearings could be on their way out.