Laws of Thermodynamics
 

I have found a really neat feature to my Monte. When the cabin gets warm from simply sitting, the rear view mirror will become loose in its ball joint. Depending on the day, it could just shake hard when I go over a patch of rough road or it gets to the point where it will be oriented differently when it finally sticks again. Knowing a bit of physics (and it goes away with a few minutes of fresh air) and given it is an OnStar mirror with some extra heft, this is explainable; but has anyone else experienced this?

Mine is getting loose in my 03 Impala also. It isn't loose enough to shift mirror direction yet - but it does get loose enough to vibrate much more dramatically than normal when its really hot out.

just noticed it (before reading this post) this afternoon actually, was over 100 degrees outside today in NJ and even with windows cracked it was well over that in the cabin. My mirror shakes with my sub bumping, but even with music off today it was noticeably shaking. Was thinking of maybe reapplying mine (gorilla glue?) once I give it a better look

I noticed that mine was loose the other day, here in Michigan it's been around 100 out all week. Yesterday i went to my car after work and the mirror had fell off the windshield and was hanging by the wires.

The placement on the windshield seems perfectly solid (at least I think) it is the ball joint that attaches the mirror to the windshield that appears to be at fault for me.