My 04 Yukon XL sometimes has a little shake at idle. It has bugged me since I owned it, but I am thinking that when I get time this summer to clean the throttle body, this might just go away. I also am going to take the time to check plugs and such to.
On my last trip down to WI, it was snowing on the way down. Got to our destination and powered off. After unloading the truck and visiting for a while, I went out to move the truck. Started fine. Put in reverse and had a racket. Kinda like a clunking noise coming from the passenger side. Nuetral or park it would shut up. Any gear and it would come back. So I parked it in its spot for the night and investigated. Ice had formed on the pass rear all around the tailpipe. In gear the tailpipe would shake enough to rattle in the ice. Knocked the ice off and the sound went away.