Strange hum from front end [Update]

"HoustonRunner" (houstonrunner)
10/26/2020 at 09:43 • Filed to: None

[Update]

Full alignment fixed it. Forgot to take a picture of the before and after report, but the toe was way off on the front drivers side.

I took it to a Firestone locally I have used for balance and alignments before. Overall pleased again, though they did call me and tell me the drive belts were “cracked” and should be replaced, but no hard sell.

Looking at the belts when I got home I don’t see any cracks, but they are certainly not new. I went ahead and ordered a new full set from Rock Auto, with 130k miles and no idea when how old they are I figured it is an easy and relatively inexpensive preventative maintenance ($105 with new tensioner).

[Original]

Overall I’m happy with the new Suburban (TL;DR - had a 2015, sold it and bought a !!!error: Indecipherable SUB-paragraph formatting!!! ).

After purchasing I was planning on putting on new brakes in front, as part of the justification was more road trips, and those will likely involve some mountain driving. I didn’t go to slotted rotors, just the coated and cryo treated Centric rotors and Posi Quiet pads.

[Short aside on that - I may try out some more aggressive pads, braking is slightly better, but I was hoping for more initial grab.]

Anyway, I noticed a very slight hum from the front drivers side (that I didn’t notice before purchase). Only seemed to be there from 25-45mph, or at least with higher speeds the road noise was louder than the hum, and the noise changed with speed not RPM’s.

My first thought was wheel bearing. There was no other indications of bearing going bad, but bearing seemed like a solid assumption.

So I decided if I was doing rotors, might as well do hubs / bearings at the same time. On the Suburban it is one integrated part, so really only three more bolts once you have the rotors off.

[Bad Oppo - this is literally the only picture I took of the process, and I only grabbed this one to remember the position of the dust shield.]

Even with 100k+ miles the process was pretty easy, only one rounded off bolt head, and since it is a GM product I was able to get a replacement bolt at the local Advance Auto.

That leads to now - the hum is still there, so it clearly wasn’t a bearing. On the plus side I have new hubs / bearings along with all new brakes on the front.

But I still don’t know what the noise is. I plan to go to a gravel lot nearby this weekend and cycle it through 2WD to 4WD modes and drive around a bit, then cycle back to see if the noise changes. It isn’t even loud enough that anyone else riding in the car has noticed it, so it really leaves me puzzled.

Other ideas?

Picture of a lizard that was checking out the living room the other day for your time.

DISCUSSION (27)

facw > HoustonRunner
10/21/2020 at 15:07

No idea here. Certainly sounds like it should have been the bearing. CV boots look good (I think the Suburban has CV axles?)?

HoustonRunner > facw
10/21/2020 at 15:09

CV boot looked good, didn’t see a lot of grease around it or notice any tears based on a cursory inspection with the hub off . Good idea to do a more thorough inspection though.

BaconSandwich is tasty. > HoustonRunner
10/21/2020 at 15:09

Any chance it is road noise from the tires? I assume alignment looks good?

Highlander-Datsuns are Forever > HoustonRunner
10/21/2020 at 15:16

Mystery sounds are never easy to figure out.

HoustonRunner > BaconSandwich is tasty.
10/21/2020 at 15:18

That was one of my next thoughts as well - planning to get a full rotate / balance / 4 wheel alignment in the next week or two.

What is pulling me away from that is - wouldn’t the noise get louder with speed? It does, but only to 45 or 50.

ItalianJobR53 - now with added 'MERICA and unreliability > HoustonRunner
10/21/2020 at 15:23

There’s clearance between the dust shield and the brake rotor ?

Try rotating tires and see if it changes/goes away.

Does it make a sound while turning?

HoustonRunner > ItalianJobR53 - now with added 'MERICA and unreliability
10/21/2020 at 15:25

I’ll double check the brake shield clearance.

Tire rotation and alignment is upcoming.

Turning has been hard to tell, as most of the time I’m going slower than when I hear the noise. Certainly does not increase in noise when taking ramps or bends at highway / off ramp speeds.

ItalianJobR53 - now with added 'MERICA and unreliability > HoustonRunner
10/21/2020 at 15:26

Yeah, I'm leaning towards tire noise/alignment right now...

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > HoustonRunner
10/21/2020 at 15:27

Your car is probably haunted.

HoustonRunner > ItalianJobR53 - now with added 'MERICA and unreliability
10/21/2020 at 15:31

Lucky for me I just checked and my Saturday morning is clear - all the kids activities are Friday evening.

ItalianJobR53 - now with added 'MERICA and unreliability > HoustonRunner
10/21/2020 at 15:33

Nice!

I would just look at the dust shield when they align the burban... assuming they have a pit there

Tripper > HoustonRunner
10/21/2020 at 15:37

I know someone else said brake shield clearance, but when I did the brakes on the Forester I had a noise (it was a scrapey noise much more easy to identify as the brakes) but it was real tough to find. Ended up being one of the tiny feet of the little metal pad shields ever so slightly touching the spine of the rotor. Sound gone.

avalonian > HoustonRunner
10/21/2020 at 15:45

If it is tires, I think Costco is doing a promo on tires right now.

Averyrm - GTI YUP > HoustonRunner
10/21/2020 at 15:45

I have a ‘16 Y ukon XL with the 6.2 . If you have it in AUTO mode, you get a hum from the front diff . It goes away in 2H. Perhaps that’s the issue?

At least mine’s always done that. I purchased it with 95k miles on it, so I can’t tell you from new.

nerd_racing > HoustonRunner
10/21/2020 at 15:46

Sounds tend to echo in cars. It is quite possible your bearing sound was coming from another wheel.

HoustonRunner > Averyrm - GTI YUP
10/21/2020 at 15:46

I’ll check that out - hope that isn’t the issue since the indicator knob is in 2WD.

HoustonRunner > Tripper
10/21/2020 at 15:47

Thanks, I’ll check those closely.

HoustonRunner > avalonian
10/21/2020 at 15:48

The tires don’t show clearly uneven wear, so I hope it doesn’t come to that.

jminer > HoustonRunner
10/21/2020 at 15:50

Lot of good suggestions in the comments, it’s harder to check/fix but I’ve had a similar hum that ended up being a diff. On my truck it never caused a problem and I drove it for 150k mi after it starte d with no issues but I got lucky I'm sure.

Averyrm - GTI YUP > HoustonRunner
10/21/2020 at 15:51

Oh, super sensitive to wheel balance as well. Especially if you have the 22" wheels.

benn454 > HoustonRunner
10/21/2020 at 16:16

Make sure to get a copy of the alignment sheet both before and after they do the alignment. Most places will be happy to oblige. If not, take your business elsewhere.

BaconSandwich is tasty. > HoustonRunner
10/21/2020 at 16:38

What made me think tires was my parent’s old Corolla. At certain speeds it was fine, but right around 50 km/h, there was a certain vibration. Above or below the specific speed, it seemed fine. It ended up being a bent rim. It makes me think something could be slightly imbalanced, and it just happens to be the right frequency to present itself at that speed.

nermal > HoustonRunner
10/21/2020 at 17:29

How are the tires? Have you rotated them since you got it? If so, try that.

HoustonRunner > Averyrm - GTI YUP
10/21/2020 at 17:35

Just the 20" wheels thankfully. I had the 22" on my old one for a while, traded those off for 20" so I didn’t have to worry as much on crappy Houston roads.

HoustonRunner > nermal
10/21/2020 at 17:36

Doing the whole rotate / balance / alignment this weekend, will report back.

HoustonRunner > benn454
10/21/2020 at 17:37

Good reminder. The Firestone I have used in the past has done good enough work, though I can’t remember if I got the “before” sheet last time.

benn454 > HoustonRunner
10/21/2020 at 22:31

At the place I work at, we show it to the customer to help explain to them what needs adjustment.