Humming / Droning Sound Over 40 Mph

EViS

EViS

Member
Our e85 has developed a peculiar humming / droning noise in the past week. I can't quite decide on which side the sound is originating from, but it does seem to be coming from the front.

The noise starts at 40mph and increases in volume with speed. It is apparent regardless of gear selection, dropping down or moving up, or cruising in neutral. Increasing revs doesn't produce the sound. There is no obvious steering vibration at speed, braking or cornering.

The Pilot Sport 4 tyres all look to be in good shape with plenty of tread left, although one tyre does have a slight nick to the sidewall which may need replacing.

Does anyone have any advice on what to look for as I'm a bit stumped what could be causing this?
 
Wheel bearings did cross my mind too. However, I was under the impression that failing bearings would whine more than they would hum / drone. Is this not correct? Is the best method to confirm wheel bearing fault by jacking up and rocking the wheels horizontally and vertically by hand?
 
99% sure it'll be a wheel bearing. but yeah, jack the car up and rock the wheel from side to side and up and down to check for play. it'll probably sound different when the wheel spins too.

also, under car noises are notoriously difficult to pinpoint - so if the fronts seem fine i'd check the rears too.
 
I believe tyres can make odd noises if they're internally damaged. If you can pinpoint a side try swapping the front tyres left to right.

Otherwise, probably a wheel bearing.
 
It does remind me when I change to winters where I hear that humming noise, just the tyre type in that case but I would not really rule out tyres.

But wheel bearings certainly sounds most likely.
 
Job for the weekend in that case. Thank you all for the super prompt replies! :thumbsup:

Are there any good guides for replacing wheel bearings? I've done this job before but that was some ten years ago on a different vehicle so I cannot really remember all of the steps.
 
Could also be a bent wheel. They usually bend on on the inside edge. Shops don't usually check for this... The BMW dealer mounted and balanced 4 new tires on my car and did a 4 wheel alignment with 3 three bent wheels. Took it to an indie complaining about the noise and they found the problem right away. Take it to a tire shop and have them check the wheels for straightness. Don't even have to remove the wheels.
 
raymond.harper said:
https://www.youtube.com/watch?v=neTiinrCNis
Click to expand...
That is perfect, thank you! I presume the rear (in case it turns out to be one of those bearings) is a bit more involved?
 
well. somewhat annoyingly, the humming/droning noise i was experiencing on the daily wasnt an easily replaced wheel bearing, it was the differential... far too much money to consider buying a new one, so going to have to risk it with a used part from a dismantler. :|
 
I don't know if this is an option for you but could you rebuild it ? If it is not the Auto 3.46 one the bearings are available. I went through the same issue and bought a replacement auto diff on the basis the pinion bearings on that one are tapers and more robust. However it turned out to be noisy as well so I have bought the bearings kit to rebuild my original one. (currently on the bench in bits) The kit I bought was £295 + delivery and vat. from www.bearingkits.co.uk. It seems to be a common issue with BMW diffs that the pinion bearings wear and from what I've read the noise is unlikely to be the crown wheel and pinion - mine certainly looked fine when I stripped it. Just a thought.
 
I recently replaced my rear differential. Found a used one for $550 with 32k miles on it. Indie installed it for $450. Big improvement. But also had a bent right rear wheel. So, I had two things causing my noise. Btw, don't overlook a possible bent wheel. Wheel was creating more noise than the differential.
 
And the humming, droning noise I was experiencing, turned out to be the rear tyre's, which had plenty of tread
Before spending serious money on mechanical items, check to see if your tyre's have gone out of shape.
 
I raised the car off the ground today and can't say that I've had too much success. I rocked each wheel but couldn't see obvious movement, but maybe I'm not looking properly (?). Trying to rock the front wheels is awkward because all of the suspension and steering assembly moves. I tried to concentrate on movement within the brake disc, but nothing was obvious.

I still feel that the noise is coming from the NSF, but cannot be totally sure.
 
Bearings can make all sorts of whining noises long before actually showing play. Spinning the wheel and listening, while trying to ignore the sound of brake pads-on-disk is about all you can do. If you're feeling particularly double jointed, putting a long screwdriver on the hub and listening to the end of the handle while spinning will let you hear better.
 
Change the fronts to the rear and rears to the front and take it for a drive. If the noise moves, it's your tyre's.
 
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