Hi guys, I know this thread is a little old, but I recently purchased a 2015 Denali, and after a few weeks I really became aware of this rattling noise. I was going nuts, buckling all the belts in, taping everything I thought could be loose down, and folding seats up/down, all sorts of combination, and for the life of me couldn't isolate the noise.
So I decided to do some online research and ran across this thread, and since I have the luggage rack option, I went downstairs and sure enough the rear crossbar shakes.
Since I do not have the correct size torx(sp?) screwdriver, I decided to use some "redneck" engineering, and basically did the matchbook under the chair leg trick. I used some black electrical tape, folded it over itself and used a flathead to insert it into the area between the bar and the cover where it bolts onto the truck.
Went for a test drive of about 20 minutes over all types of road and areas where I knew the rattling was the worst, and VIOLA!!!!
Worked like a dream, no noise, no rattling at all. The truck is whisper quiet now and feels like it justified it 75K+ price.
Nothing worst than paying a price that could have gotten me into a high end German vehicle, only to have it rattle like a Yugo.
Now I drive with pride, lol.
Anyways thanks guys for the help, because this was driving me nuts.
