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Noise At 60-80 Mph



I've got a friend with a Z-66 truck that has some noise right at 65-75 mph. It is brand new with only 500 miles on it. The noise is a humming sound in the cabin that doesn't start until after 60 mph and goes away above 80 mph. There is no vibration in the steering wheel or foot pedal, but the hum is unmistakable.

Has anyone else encountered or conquered this problem?
Heh heh heh - I have - and here is a totally wild guess because it wasn't on my Avalanche.

When I picked up my Pontiac Montana back in 1998 I had a similar issue. A vibration or hum sound at highway speed - damned if I could figure out where it was coming from. I even pulled out every seat emptied the damn rig and took out - still made the noise.

Took it to the dealer and they spent all day with two guys trying to figure out where it was coming from. Turns out that one of the cross supports on the roof rack was vibrating in the wind making the noise. They replaced the piece and it was fine after that.

There is my wild guess...
The truck doesn't have a roof rack, but the assist steps are an unlikely candidate. I don't believe the hum could be radio related because the radio is off and driving between 60 and 80 turns the noise on every time and driving below 60 and above 80 turns it off every time, so it is definitely speed related.

The best example I could make is if you have a sunroof (which I do, but my friend doesn't) and pull the wind deflector down while traveling at 35 to 45 mph, you get an incredible body boom. This noise is not that annoying, but it has many similarities.

I have the same hum. Mine starts at about 45 mph and stops at about 60 mph. I have tried to locate it by opening windows and listening. Best I can determine is that it is coming from driver's side rear. Sounds like a wheel bearing (just a guess). It hasn't gotten any worse since new. Have 5500 miles on Z66. Seems most annoying with windows up, radio off. I figured to wait a while and see if it gets any worse before going to the dealer.
Could it possibly be related to the driveshaft imbalance? If you mention wheel bearings, I'd also have the dealer chack the driveshaft and it's u-joints.

Just guessing, but I have seen some antennas cause similar issues. :C: ??? :rolleyes: :eek: :0:

I will throw in my 2 cents - does your friend have a bug deflector? If Yes, there are many post with the solution.

I have a similar hum and have'nt found the source yet. I also have a hissing noise at city speeds that goes away when you come to a stop- sounds like a gas pump, but it isn't . Any ideas on this one?

Blue, the noise you are referring to is a flapping noise, different than the hum. CAFCNA mag has the solution for that one.
I forgot to mention that when I am driving along at "hum speed" - if I let up on the gas, most of the hum (80%) goes away. I can still hear a very slight hum while off the gas. As soon as I'm on the gas, the hum is there. Hhhmmmmmmmmmm!
The fact that the noise goes away for the most part with the gas off says driveline...possibly ring and pinion gear. Although that noise is more noticable at 50-65 mph. I had an AV that had the R&P gears replaced and the noise went away for awhile only to return again. On my second AV and the noise is also in this AV. Not as bad but eventually I will take it in. I have a couple other noises, any help would be appreciated.
1. When going though the gears as the rpms rise I hear almost a sqealing noise that increases as the rpms go up...then stops when it shifts up. Wasn't there in my first AV.
2. Wind noise in drivers side window that started after I had the front windows tinted. Do they remove the windows to do that? Can't honestly remember if it was there before because I went straight from the dealer to the tinting guy.
3. Clunk at time in the rear locker with low speed acceleration in 3rd. Sometimes subtle...sometime fairly loud.
I am saving up noises for one big trip to the dealer...any info would help. Thanks.
:ideaProblem Fixed!!!? ???

OK-Thanks for all of your input and here is the latest. On Thursday, Dave (my bud) took his truck to his dealer (remember it only has 500 miles on it). They drove it and heard the sound and said they would replace the driveline. I think they had another truck or two that they had a similar sound and repair.

Friday, the dealer said the noise was gone. My friend picked the truck up after work and so I will find out on Monday the outcome. If it worked, I will post the detail of the problem, how to differentiate it from other noise and the warranty work the dealer did on the truck.

Hope this helps, and thanks again. Stay posted! (y)
I have a 03 z66 2wd with 5.3 L. The humming is exactly what I have too. It starts at about 50 mph and quits at 70 mph. The pitch of it increases as speed increases and the volume of it increases with acceleration. 300 miles so far. I had an S-10 pickup that made a similar sound from 60 mph to 65 mph that was present when new and now 8 years later the sound is still there unchanged.