Driveline hum/noise - diagnosing? RESOLVED

[g300d]

Guys, what's a good procedure to diagnose driveline humming?

Accelerating up to 50, it starts to make a bit of noise. It's a muted humming that changes with acceleration and deceleration, becomes unoticeable below 40 or so.

Subjectively, the car does not "roll" on the road as smoothly as I would like.

No driveline vibration, it's more of noise.

Sound does not seem to vary when doing side to side transitions so it doesnt seem to be wheel bearings.

Any other checks to do to rule those out?

How about the diffs/propeller shafts, what's the best way to see if those are the problem?

X5 3.0 on staggered 19" sport package wheels and tires, tires are OE Bridgestone Turanzas.

RESOLVED: Rear wheel bearings

[nicolaerugina]

Have u notice this noise after changing the tyres?
I had the same noise with a set of Bridgestone tyres. After replacing them, the noise go's away!

[g300d]

When the tires were new there was no noise so I am not sure if it's the tires. Still very thick tires, definitely more than half tread life left on the fronts, maybe 70% rear.

[nicolaerugina]

I am saying that, on my case, a new set of Bridgestone tyres was the problem. The tyres been in warranty, I replace them after a week with Goodyear and the noise was solved!

[electricalserv x5]

sounds like wheel bearings ,I had the same thing.

[Ricky Bobby]

If it's above 40 mph, and unnoticeable below, probably wheel bearings. Tell tale sign is taking turns above 40, it will quiet down depending on what side the bad bearing is, and which way you are turning.

I would replace in pairs if it is wheel bearings, as good practice.

[g300d]

Originally Posted by nicolaerugina

I am saying that, on my case, a new set of Bridgestone tyres was the problem. The tyres been in warranty, I replace them after a week with Goodyear and the noise was solved!

Ah, gotcha!

Originally Posted by electricalserv x5

sounds like wheel bearings ,I had the same thing.

Originally Posted by Ricky Bobby

If it's above 40 mph, and unnoticeable below, probably wheel bearings. Tell tale sign is taking turns above 40, it will quiet down depending on what side the bad bearing is, and which way you are turning.

I would replace in pairs if it is wheel bearings, as good practice.

Ugh...saw that wheel bearings are not the easiest to do on these.

Yup, if these are it, will change in pairs definitely.

EX5, did you change front, rear, or all wheel bearings?

RB, I took a long sweeper at speed and I did not notice a change though. Will have to make a test run to be sure.

Any other ways to confirm its the bearings?

[g300d]

Update:

On the road, the "driving on a metal bridge" sound starts at about 40-50mph, then gets speed dependent.

Very noticeable at decel at around 50mph or so, then progressively gets less noticeable. Below 40 it's pretty much gone.

Seems to be from rear, while driving I tilted my head back between the front seats and the sound gets a bit more distinct.

Tried swerving left to right and taking sweeping turns at speed to unload bearings, no change in sound.

[g300d]

Update 2:

Put the car on stands and spun and shook all the wheels.

Fronts were fine, found a few issues at the rear.

There was movement when shaking the rear driver side tire and we thought we found our damaged bearing...turned out to be a failed upper wishbone ball joint though. Both l/r upper locating link ball joint boots were torn as well. So l/r upper wishbones and upper locating links are being replaced. These would not be causing the "running on a metal bridge" sound though.

Spinning the rear wheels there was a bit of clicking that seemed to be coming from the diff. Nothing obviously wrong with the bearings. Decided to replace them anyway as a best guess first step.

Bearing removal was pretty unremarkable considering the horror stories, unbolted from the rear of hub and pulled right out.

Spun the removed bearings by hand and not obviously worn at first, but putting a bit of pressure on it while spinning I could feel a slightly rough portion of rotation on on the passenger side bearing. It was nit picking though, they both felt serviceable to me.

Pressed the old flanges out to be transferred to the new wheel bearing assemblies. The bearing covers of the old bearing fell off during the process and got to look at the bearing's guts. Balls looked fine and there was still grease inside.

I got SWAG brand bearing assemblies. They use Koyo Japan-made bearings. For reference, the original bearings were Koyo's as well but made in the USA.

Rear discs were off so adjusted the parking brakes as well, they were getting a bit loose.

TL;DR: nothing obviously wrong with rear bearings but replacing both to start. Busted left rear wishbone ball joint, torn ball joint boots on l/r locating links, so replacing both parts in pairs. Adjusted parking brake.

[g300d]

Final Update:

So replaced upper wishbone, upper locating link, and wheel hub bearings in pairs.

Alignment was performed. I had the alignment checked when I first got it at 25,000 miles and the rear camber was at 1.5deg or so, which progressively got steeper over time to a bit over 2 deg. At my last alignment at 40,000 or so (after front suspension work), the best we could get rear camber to was 2-ish deg.

I was glad to see we could now get rear camber back to 1.5deg. Toe front and rear was set to around .05 or so.

Went out for a test drive and I'm glad to hear (or not hear) the "running on a steel bridge" sound is gone!

Looks like it was the rear wheel bearings as many have shared.