Cannot be tighten, replace the mirror assy..
On the door there should be a triangular panel that you can carefully pry off which is located right where mirror attaches to door and after you remove you can see screw/nuts.
It definitely depends on the year, but on 1988 through (I think) the late nineties trucks with manual mirrors, there is a cover on the base of the mirror that pops off (be gentle because the tabs will break off if you don't treat them nicely). Under that cover there is a plate with a screw in it that you can tighten to keep the mirrors from swinging in. If you have to tighten the head of the mirror (a.k.a., the mirrors falls downward), then you have to take the mirror glass off - I think there's a similar mechanism inside of the mirror head (it's been a while though).
You have to remove the plastic piece in the inside of the car which will expose the bolts to tighten the mirror
how do I replace 307SW wing mirror
unbolt the mirror from the car and look inside the mirror for a bolt to tighten, don't remember if it can be tightened or not.
Jeep cherokee
take off the inside panel and tighten the mirror. I did it and it is easy once you get the panel off which is not so easy.
Pop off the plastic cover on the back of the mirror. Then release the mirror by sliding the mirror forward. Then you can see the mirror bracket and the loose screws. Tighten the screws and replace the mirror. It takes about 2 seconds when you know what your looking for!
To tighten a loose side view mirror on a 2002 F150, take out the old screw and screw in a slightly larger one. It is also possible to tighten the mirror by using plumber's tape around the original screw.
If it's the brackets mounting the mirror to the door, you have to take the trim off the door and tighten it from the inside.
You will need to remove the door panel of your 1997 Chevrolet Corvette. When the door panel is removed the mirror retaining bolts will be visible. Tighten the mirror retaining bolts.
* Remove the mirror trim cover from the door panel * You will see three retaining nuts check/tighten them