Side mirror problem
 

I have been having a problem with my mirrors. when I adjust them they seem to slip, I'll hear the motor move but the mirror wont, then I hear a snap and they start moving. sound like somthing is stripped I though. also, they vibrate and rattle. can this be cured by just tightening the mirror to the door? they do seem a bit loose. anyone else had to do this?

Also if anyone knows of a "how to" on tightenong/removing the mirrors, that would be great . thanks