Rook126

If you haven't already seen this, here's an old post with some opinions for you.

Here's a pic after applying the seam sealer. The sealer was glossy black. Blue painters tape was used to prevent any spillover onto the outside of the rear glass. Also, notice the circular rings of 3M windshield butyl tape I place around every bolt hole for the spoiler. I didn't trust the original foam washers that were deformed under compression when the spoiler was bolted from the factory. If you are not aware already, this is a common problem that many have already posted about on this forum.

Taken from the outside looking down with the spoiler removed.

Here's one of two fractures I found on the brittle plastic frame at the top edge of the rear glass. Repaired it back in December with a tube of 3M Urethane Seam Sealer, 08367, Black Color and it never leaked again. Just run a bead of this self leveling sealer alone the entire length of the plastic frame so water will never settle in the channel.

I'm steering toward a heat shield as CamGTP mentioned. This might not be the source of your noise but it was for my 2020 Sierra.

Do what dram mentioned above and try the rear first. You will notice a big difference in the handling at high and low speeds. I have the Hellwig bar on the rear and stock on the front and I'm still happy the the purchase.

Get the 11mm versions instead of the 6mm which were not very bright when I first tried them. They were too dim to illuminate the interior so I ended up with the 11mm installed. See the link to the Interior Lighting thread above from Bikerjon.

Don't invest too much into the door speakers. The Bose system limits the frequencies to the doors speakers and you'll get mostly mids and muted highs. The 2 way Kickers in my doors sound flat. Same for the rear door speakers but they are even lower in volume than the front doors at the same volume setting. Invest in some larger tweeters for your dash with the right capacitor to give you clear mid/highs. This will balance out that sub output. I'm run a 10" Solo-Baric. When running this set up, I have the radio's bass set at full negative and zero for the mid and treble. No muddy bass but it gets fairly loud inside the cab.

I drive the same year and Denali trim you mentioned. I mainly use a Bluetooth connected iPhone for my music but I also have been using a stubby 128gb SanDisk USB drive that is left in the USB port under the center console lid. Formatted in FAT32. Amazon still sells it for $16. SanDisk 128GB Ultra Fit USB 3.1 Flash Drive - SDCZ430-128G-G46 There is also a 256 and 512 but I don't know if they will work. You can rename your USB drive and that is what will show up on your screen as a music source. I have noticed it spending 30 seconds to a minute indexing all of the files after you first plug it in and power the radio. Music from the drive will play while it is indexing but you just can't navigate to other songs until it is done. Note that the larger drives with more files will likely take more time to index. iTunes already organizes all of my music files into folders named after the artists. I just went to the folder where iTunes stores all of the media and copied every artist folder onto my SanDisk USB. I haven't experimented with creating playlist so I'm not sure how that is done but the option is available on the touchscreen. Music is sorted by song, artists, genre, album, etc. Play anything you want or just shuffle it all. Song information displays just as it does while play from your phone and the album art displays on the screen if you have that too.

Could your lugs be "Splined" requiring this FUEL Splined Socket Key? Only $5 in this link. https://fueloffroadutv.com/products/spline-key Here's another image from this site. https://agileoffroad.com/product/agile-splined-lug-nut-key/

Here's a thread that might give you some additional information.

I resolved this noise a couple months ago but my post did not get much attention. Here is how I made it go away forever.

For those who are still having this heat shield noise issue, I wanted to let you know that I have not had the noise for the last couple months so I believe it is now resolved on my vehicle.

As with many of us, this buzzing vibration noise has been eluding me for months. It sounds like a heat shield or thin metallic sound just as some of you have described. I typically only hear it randomly at very low speeds and rpm such as when I am turning into a parking space or reversing slowly. I'm certain it still happens at higher speeds but I don't really notice it because of wind/road noise or the music being turned up. I've seen the other posts mentioning the heat shield at the spare tire and leaf springs but this was not my case. I went back under the my 2020 Sierra today and combed over it inch by inch, plucking and hammering around. The heat shield at my spare tire seemed fine and didn't have any clearance issues with my GM performance exhaust pipes. I made it up to the fuel tank and finally replicated the buzzing sound when I hit the plastic tank. I discovered the buzzing vibration sound was coming from the fuel tank heat shield on the driveshaft side. I reached up to the top of the heat shield and bent it at the top slightly away from the tank and the noise is gone whenever I hit the tank. I initially flexed it too far and popped out one of the plastic retainer clips. It was easy to reseat the clip. I haven't been able to replicate the noise for now but only time will tell. Listen to the video clip to determine if your noise is similar. I have not come across a post about the fuel tank heat shield yet so I hope this helps some of you out. buzz.mp4

The Hellwig rear sway bar is expensive but well worth it to me on my 2020 CarbonPro Denali (non-AT4). It was my best upgrade/mod and I immediately noticed the improvement in handling and lack of lean during corners and quick lane changes. I still have a stock front sway bar that works just fine in conjunction with the Hellwig rear. Hellwig makes are rear bar specifically for the AT4 with the higher suspension than mine. Here's my previous post on the install if you haven't come across it already. '