GMC denali yukon 2022 mysterious noise sounds like something hits underneath car behind drivers seat

WalleyeMikeIII said:

Got any loos items stored under your rear floor in the cargo area. My dealer threw the lug nuts in there after installing the locks…and they made noise under certain stops/turns, etc. I actually lined my under floor storage with neoprene (mouse pad like material) from the fabric store.

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No, I dont. And again, mine is a heavy thud. Nothing metallic about it.

Just a thought…. Even though @KMeloney said no engine replacement in his truck, not a bad idea to check the transmission cross member bolts.

I say this as when I did my last oil change on my 2006 XL a few months back, the filter fought me coming out, and going in as it always does. I was so fed up that the K&N “easy install nut” on the bottom of the filter still didn’t have enough room to clear a socket properly secure on the nut to remove with a ratchet on it that I pulled the cross member out to make room and get the filter out. I snugged everything back down proper when I reinstalled it after the filter went in, but last night while doing my oil change, the bolt on the drivers side of the cross member was over halfway loose and the crossmember could travel quite a bit up and down on that side. I didn’t notice any abnormal noises but that doesn’t mean it wasn’t making any if the crossmember was moving. I’d imagine though that sitting in the drivers seat and hearing that cross member slap around, it would sound as if something was hitting the underside of the truck just to the rear of the drivers seat area.

I am glad someone has this issue. I have a 2023 Tahoe RST 6.2 and hear the same thud coming from under the rear seat area. I installed a sub last year and thought maybe that was it… like a loose wire or something making it pop. That’s not it though. I need to bring mine in for a recall. Gonna ask them to look into it. Worries me when I hear it. Problem is it’s just so random.

337Bengal said:

I am glad someone has this issue. I have a 2023 Tahoe RST 6.2 and hear the same thud coming from under the rear seat area. I installed a sub last year and thought maybe that was it… like a loose wire or something making it pop. That’s not it though. I need to bring mine in for a recall. Gonna ask them to look into it. Worries me when I hear it. Problem is it’s just so random.

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Please keep us posted!

Maybe don't direct the techs to a certain area of your truck where you think you hear the noise. I directed the tech to look somewhere around the rear axle, but I don't really know that the noise it coming from there. It might actually be coming from somewhere up front, as others have experienced. But we're all not losing our minds, I'm sure. Someone has to be able to track down the source -- and maybe that source in my truck will be a crossmember bolt being loose, too.

My 23 Yukon SLT definitely has something similar happen around just behind the driver’s seat from time to time. Almost sounds like a nut rattling around. Happens very infrequently.