The drivers side door mirror glass(not the whole unit,just the actual mirror itself ) is loose & vibrates when driving.how/can? you tighten it up?

Either it's a cheap replacement mirror that can't be tightened. Or, the original (oe) has been hit hard enough to displace on of the plastic attachments behind the mirror. Adjust the mirror to the extreme right so you can peek behind the mirror to look for an displaced attachment. Line the 2 points up and firmly with a gloved hand, push into place until you hear it "click" into place. Good luck

02 GMC Sierra outside mirror.my mirror shook driving down the road.i simply pushed the mirror down to get to the tangs with a screwdriver and cleaned the back of the mirror with alcohol in 2 opposite areas just next to the tangs and applied a 3m strip of double sticky back foam then pressed it firmly back on the mirror housing.that took all the sack out.you can test it prior by pushing the mirror down and look in the gap with a flashlight,wiggle your mirror while looking back there to see where the gap is and how much tape you will need.you can double up on the tape if need be.hope this helps someone.there were no answers for my questions