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Discussion Starter · #1 ·
My 2020 GMC 2500 HD Denali with Duramax which just barely exceeded 10,000 mi this week (last week of July 2021), makes a humming sounds that has gotten worse. Took it to the dealer, all they said is that it was not the wheel bearings and they gave it back. So, feel like I have to “help them” find the problem.

Symptom: when not towing (no load other than yours truly), the humming starts at as low as 25 mph. The pitch of the hum increases at increasing speed, but is not related to engine speed or gear. When towing a 10,000 lb trailer, I hear the same hum, but not until around 45-50 mph. So the problem is related to speed and is affected by the load. That makes me think it is somewhere after the transmission, in the drivetrain. U joint? Carrier bearing? Differential? The damn truck only has 10,000 mi. Any thoughts?
 

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Tires are responsible for any unwanted noises. Just an idea.
 

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Discussion Starter · #3 ·
Tires are responsible for any unwanted noises. Just an idea.
Yeah, I pulled out the spare yesterday to attempt to see if swapping out a tire would change or eliminate the sound, but unfortunately I don’t seem to have the correct lug socket to change my own tire, which pointed out another issue to correct haha. (I have aftermarket rims and THOUGHT I had the socket I needed, but apparently I do not.) So that little test will have to wait, but will be done.
 

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Is the spare tire the same size?
 

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Discussion Starter · #5 ·
Is the spare tire the same size?
Spare is on an 18-in rim whereas the others are 20-in. So not the exact same tire. I did finally do my spare test. The previously unused spare did not change the noise. I then had my wife drive the truck and I rode in the truck bed. I leaned over the sides to listen to the tire noise and the sound didn’t seem to be coming from there. The sound was coming from right below me. I pulled the plastic covers to the gooseneck-ready ports in the bed to try to hear even better, and became convinced this was a mechanical sound, not a tire sound. And the sound seemed right in the middle of the truck. So I think one of the u-joints or the differential is the problem. Gonna go back to the dealer and make one of their mechanics ride in the back like I did.
 

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Discussion Starter · #6 ·
Finally got this issue resolved. It was, in fact, a rear wheel bearing. The annoying thing is that, as mentioned previously, I had it at the dealer and they supposedly checked the wheel bearings and said they were fine. Apparently, they only checked the front bearings and not the rear, which is really annoying because I always said the sound was coming from the rear. I made one of the techs ride in the back of the truck, and he then knew there was definitely a problem. So they checked the rear bearings this time and, gee, there was a problem. The replaced the bearing and the noise went away.
 
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