Hum sound while driving

[dougl122]

Hello. I've got a noise I'm trying to diagnose. 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.
Seems to be tied entirely to the speed of the car, not related to RPMs, throttle, etc.

Any thoughts?

 

[dougl122]

Forgot to mention, it's a 2010 Cobalt.

 

[YelloEye]

I had a speed correlated sound that I thought was a wheel hub. Turned out to be a starved bearing for the 5th gear transmission shaft.

Put the nose on jackstands or on a lift and have someone put the car in gear to determine where the sound is coming from.

 

[roosterk0031]

Jacked up one front tire other on ground, E brake on, start engine and put in gear, the tire in the air will spin (unless you have a limited slip), spin in up to 35 or so, if no noise, repeat with other side.

Swerving while going down the highway will change the sound that also points to wheel bearing and can be used to identify which side. (but I've replaced a passenger side on twice when I was sure it was it again, only to have to install the one I just removed on the drivers side), tire in the air is a better method to identify which side, swerving to help identify wheel bearing.

 

[john intili]

you can jack up the car, remove both wheels in fron, and spin the rotor with two fingers grip a coil on the spring, if the bearings are bad you will feel right away!

 

[ironwill11]

Hello. I've got a noise I'm trying to diagnose. 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.
Seems to be tied entirely to the speed of the car, not related to RPMs, throttle, etc.

Any thoughts?

Can you isolate if it is coming from the front or the back of the vehicle? How many miles are on it? My wife's 2007 had 215k on it and we noticed a humming coming from the back. It was hard to distinguish which side until we drove it long enough and there was some vibrating from the driver side rear wheel. Replaced both rear wheel bearings and was good to go.

Will

 

[mjb]

After I got my car, had a "grinding" type sound, thought it was the bearing. Replaced one of them, didn't help. Turned out it was just worn/bad tires. New tires, sound gone. Stay away from the cheap ones, not worth it. I'm running on Pirelli's for 4 years now and still plenty of tread.