wcgman

My 10 picked up that really annoying buzzing/rattle from the rear view mirror probably about 12k miles (4k miles ago). Some days worse than others, but can make it happen consistently between 80 and 85.

I found by lightly touching the power connector on the back of it, the rattle went away. So today I grabbed one of the soft felt velcro cable tie wraps from work (usually for CAT5 network cable, etc...) and wrapped it fairly lightly around where the power coupler goes into the back of the mirror and the rattle went completely away.

If you cant get them at work, you can find them at office supply stores like office max/depot and walmart target. Just look for cable wraps that are the velcro ones and softer material. I found one the perfect size, but a larger one can be trimmed to fit easily and you cant see it at all.

Mulepick

I applied some clear silicon around the mirror plug making sure not to get any into the female electrics. Plugged it back in and after 2 days all rattle is gone except for some slight rattle over the roughest road. All this at 29 degrees.

rt66er

I fixed mine by yanking it out and installing a manual dim mirror. The auto dim never worked to my satisfaction; too slow to dim and it never got dim enough for my taste. I lost the compass function, but I pretty much know which direction I'm goin' anyway.