Faint buzzing noise coming from the rear.

[a8starr]

A few months back I noticed a faint buzzing sound whilst sitting in the back. Now that I know the sound I can always hear it whilst in the drivers seat.

I notice the buzzing sound starts at around 58-60mph.

The pitch of the buzz increases with speed.

The buzz sound doesn't change when the road surface changes. It's a very consistent sound.

I have read around and gathered that is could be the tyres, wheel bearings or fuel pump.

What are your thoughts?

[EG-4.0TDI]

Or rear differential... Does it change depending on load? if you were on an empty motorway and made a sharp lane change to the left or right, does the noise increase during the move? If it does it is probably a wheel bearing. if it doesn't you're more likely looking at rear differential or prop shaft centre support bearing.

Does it do it under acceleration, deceleration, or both?

[a8starr]

Ok thanks. I will try that. How much are we talking for rear differential or prop shaft centre support bearing? Car is only 82k on clock.

[a8starr]

Does it do it under acceleration, deceleration, or both?

Sound is only noticeable over 40mph and its very quiet. if decelerating sound also occurs but will become lower in pitch until it's disguised by engine noise/ road noise once 40mph or below is reached.

[EG-4.0TDI]

My diff went with about 90k on it - there is a known issue with the carrier bearings in them on the V8s which may have the same set up as the V6s. Main dealer rates mean the part is about £4k and fitting is about three hours so fingers crossed it's not that! If it is the diff it would be worth looking at vehicle breakers but make sure it's the later version of the diff.

Not sure on propshaft but if it is, you can't get the centre support bearing on its own - ie it's a whole propshaft but I don't know how much.

[a8starr]

Could it be anything to do with my parking brake? I sometimes get a fault with it but it goes away. The sound is very very quiet. Only noticeable to a sensitive ear.

Could 1 wheel bearing resonate through the whole car? At what mileage do wheel bearings usually go?

Sent from my Nexus 5 using Tapatalk

[EG-4.0TDI]

Not sure about parking brake, but wheel bearing is definitely a possibility for what you're describing - hence try the weight transfer trick and see if the noise changes. Also worth checking your tyres don't have any weird wear and that the wheels are balanced.

You can also jack up each rear wheel (put air suspension in jacking mode first) and check for play. Next step if that doesn't yield a diagnosis is to get it run on a pillar lift and listen with chassis ears to confirm if it is road or drivetrain related.

If you search back you'll find my diff related post which outline the diagnostic steps I ended up going through to rule everything else out.

Good luck and keep us posted!