The rearview mirror on my 98 LX has been loose for as long as I can remember, so took it apart today to figure it out. The mirror had never been removed as I still have the factory windshield. Should have taken pictures, but I was able to fix it so quickly.
The single phillips screw on the under side of the mirror was extremely tight. It seems like anytime Toyota uses a Phillips head, it's always tight. I put the screw driver down before stripping it out, since it wouldn't budge. I used a t-handle driver and a Phillips bit that fit the screw tightly to remove it. The mirror came off with a silver hook clip that holds the mirror onto the mounting plate, I let the mirror hang at this point. I tightened the two screws on the metal mounting plate on the windshield and then reassembled everything. Problem solved.
The single phillips screw on the under side of the mirror was extremely tight. It seems like anytime Toyota uses a Phillips head, it's always tight. I put the screw driver down before stripping it out, since it wouldn't budge. I used a t-handle driver and a Phillips bit that fit the screw tightly to remove it. The mirror came off with a silver hook clip that holds the mirror onto the mounting plate, I let the mirror hang at this point. I tightened the two screws on the metal mounting plate on the windshield and then reassembled everything. Problem solved.