Humming sound at higher speeds - 2010 Cobalt


#1

Hello. I’ve got a noise I’m trying to diagnose on our 2010 Cobalt. Thought I’d ask about it here before heading to a mechanic.

When I hit about 35 mph I start to hear a hum sound that we’ve never heard before (my wife says she can here it at slower speeds, but I can’t).
The sound gets higher in pitch as the car speed increases. The RPMs don’t affect it (i.e. when the car shifts gears, no change in the sound).
If I shift into neutral and take my foot off the gas, the sound doesn’t change (except dropping in pitch as I slow down).
Seems to be tied entirely to the speed of the car, not related to RPMs, throttle, etc.

Any thoughts?


#2

You don’t give us much to go on. I am making a guess based on what you’ve told us.

Let me ask you a question… Do you rotate your tires? Have the rear tires been on the car (and on the rear) for a long time?

If the answers are No and Yes, the noise is coming from your rear tires. It is telling you to replace them no matter how much tread they have left. Tires deteriorate with age and use even if the tread isn’t worn off. They get harder, lose traction and get very noisy as time goes on.

A very common error front-wheel drive owners make is to not rotate tires and only replace the front tires since they wear out much sooner that the rears. This is an unsafe practice.


#3

I agree with mustangman’s recommendation, but if it turns out to not be related to the tires, I think there is a possibility that the noise is coming from the differential. When you have the tires rotated, why not have the differential lube checked?


#4

Does the pitch of the humming change when changing lanes or turning? If the sound changes that is an indication of a bad wheel bearing.

Ed B.


#5

We rotate pretty regularly - usually when we get an oil change, so about every 7500 miles. I’ll have them rotated and balanced today and inspected at Discount Tire. Unfortunately they’re pretty limited on what they can inspect.

I haven’t noticed it changing while turning or changing lanes, but I haven’t driven it at very high speeds, so my turns are usually slow enough that I can’t hear it it all. I’ll pay attention to that next time.


#6

My vote is for a wheel bearing. When they have it on the lift, have them manually spin the wheels and check for noise. That is not a great test, but it may tell you something.


#7

Agree with @BillRussell on that.

Bearing would be my next choice based on what you told us about the tires. The little ones in the rear might make a higher pitched sound. Typical bearing noise is a deeper rumble type noise that rises in pitch with speed.


#8

I vote wheel bearing.

I just replaced the hub/bearing assembly for the exact same noise on the son-in-law’s 2011 Malibu.

Tester


#9

My old VW Rabbit started having a little bit of humming noise like that, only at freeway speeds, which I of course ignored. It progressed over time to more of a growling, in the end it was a pretty loud roaring noise at anything over 60 mph. Front wheel bearings in my case. As posted above, tire inflation and unusual wear patterns is the first place to look. Transmission/differential fluid levels too.