I have a 1997 2.8 too, with the same vibrating driver's rear view mirror. The dealer got the mirror assembly replaced (and painted) under warranty. It stayed good for about a month... but the vibe returned. Guess I'll just have to live with it. I cannot feel any "looseness" difference between the left and right mirrors when stopped and inspecting manually. I'm toying with the idea of putting some soft styrofoam behind the mirror.