Just slam your fist on the dash, that typically elliminates the rattling

 

That was one of the first things I did, wife thought I was going crazy. Needless to say, it didn't work.

 

Mine does the same thing

 

My 14 noise was where the plastic dash was coming in contact with the base of the windshield. I shoved a piece of felt in there to separate them and it worked. I still get some type of rattle in the dash at high speeds on a windy day.

 

Get the same chit on my LMM. Radio goes up.

 

I had the same issues on my LMM but got everything fixed. Found a few things. The control module in the lower dash for the electric brake was loose in the panel. Used some adhesive foam around the edges and reinstalled it. Second, the trim panel just under the steering wheel. There is some metal backing to the plastic face plate. I pressed on the metal backing plate and everywhere the metal would touch the plastic I would get under there and work in some RTV. Finally, the worst vibration was in the winter at idle. Once I put on a lift pump (FASS 95) the idle smoothed out considerably. Now as quiet as a Caddy. Dean E

 

I got most of it out by jamming some small diameter rubber hose in there.

 

^X2. It wouldnt be a GM if the dash didnt rattle.

 

Ok, I know this thread is over a month old, but figured I'd give an update in case anybody else starts having this problem. Finally had the chance to drop it off, it took the dealership 6 days find the problem and they had to call an engineer in to help them out. They said it was a "rivet" behind the instrument panel that is there to hold in the info screen for the Denali's, mine is an SLT, so obviously this "rivet" is not used in my truck. So if anybody experiences this noise, tell your dealership to look for that "rivet" or "rivets", don't know how many there are.

 

Great to hear they found the issue and thanks for responding. It is always great when a thread is completed with the issue resolved and more knowledge out there.