2014 Sierra humming noise

[Oli4]

Hi all

New member here from Canada.

A month and a half ago I took possession of a brand new, factory ordered 2014 Sierra All Terrain. Fantastic ride.

There's one thing that concerns me though. And I really don't have an idea what it can be. But this engine makes a rhythmic humming noise when driving at highway speeds (105km/h, sorry we are metric).

Humming lasts for 1 sec and then 1 sec of silence, 1 sec of humming, 1 sec silence and so on.

Doesn't matter on or off the power, or in v4 or v8 mode. So it's speed related not rpm related. Goes away when slowing down and cross the 95km/h mark or so.

I've tried pretty much everything. Even turned airco off thinking it might could have been the fan. No dice.

It's subtle but the wife picked up on it too.

 

So what could this be? Any ideas? Looking fwd to every suggestion I get on this forum.

Thank you.

[clayp]

sounds like it could be your tires or differential if it is related to speed and not engine RPM

[pm26]

Yes, if it is a subtle whine, it could be the differential. Does it make the sound only while under power, or only when coasting? Could be that the differential gears have slightly improper backlash setting.

[Oli4]

Sound happens under power and while coasting. Doesn't matter what gear I am in.

Goes like this.

XXXXXXXX__________XXXXXXX________XXXXXXXX________XXXXXXXX

 

XXXX=hum and lasts about 1 sec with 1sec pauses in between. Really weird.

[Oli4]

Update on the humming noise. If I shift it to 4x4 auto, the noise disappears. If I shift it back to 2x4 noise gradually comes back.

[1kwik72]

Sounds like it could be a second order harmonic from the driveshaft. Putting it in 4wd may load the transfer case and or axles differently and keep it from resonating. If I remember correctly there is a TSB or PI that has some info on driveshaft vibrations.

[1kwik72]

I just looked the PI on the driveshaft/u-joints was for low speed vibrations 30-35mph

[Boot]

Update on the humming noise. If I shift it to 4x4 auto, the noise disappears. If I shift it back to 2x4 noise gradually comes back.

Mine does the exact same thing and I came upon the exact same solution. Turned dial from 2x4 to 4x4 auto and it went away. Now why was it doing it in the first place. 2014 Sierra SLT 2200 miles.

[Boot]

Update on the humming noise. If I shift it to 4x4 auto, the noise disappears. If I shift it back to 2x4 noise gradually comes back.

Mine does the exact same thing and I came upon the exact same solution. Turned dial from 2x4 to 4x4 auto and it went away. Now why was it doing it in the first place. 2014 Sierra SLT 2200 miles.

[Oli4]

1kwik72 That's exactly what I though too. That it was a harmonic from something vibrating. But yes it is high speed only. But 30-35mph is about HALF of the speed I am getting it at (65mph). If this is a vibration then it will naturally occur at different frequencies too. Maybe that's what I am experiencing. Your thoughts?

I'm glad I'm not the only one though Boot. I thought I was loosing my mind.

[1kwik72]

_{Typically a driveshaft or u-joint will have a "sweet spot" where it hums/vibrates/throbs depending on weather it is an imbalance issue, a phasing issue or u-joint issue (seized damaged or off center) We are old school here at my shop but your GM dealer should have equipment (and training) to isolate the frequency of the vibration. It could be as easy as swapping the driveshaft 180° in the yoke or maybe it wasn't balanced as good as it could have been or lost a weight. Not sure as I have not looked at a 2014 driveshaft but GM generally holds their u-joints in with a thermoplastic that locks the joint in place. If it was damaged or the joint was not perfectly centered in one of the yokes even by a small amount it would set up a harmonic.}

 

_{Another thought that we see all the time is mud and or snow on the inside of the wheels. Even a little bit will cause vibrations and or shaking. Haven't tried out it's mudding capabilities lately have you?}

[Oli4]

It is not a vibration. I can't feel it in my steering wheel or in my butt. ;) It's just a noise 1kwik72.

[1kwik72]

It is not a vibration. I can't feel it in my steering wheel or in my butt. ;) It's just a noise 1kwik72.

Driveshaft imbalance can cause a sort of hum as quiet and smooth as these things are it wouldn't take much to be noticeable.

[Boot]

I'm still dealing with this, is anyone else? I'll be taking it to the dealer when I'm due for an oil change and have them check it out.

[Oli4]

Same here. But. Here's an update. It goes away when trans temps reach normal operating temperatures 90C. Did a long trip over the weekend and it went away. It's back now though.