This is what was under the original mirror on the left side. They turned out to be threaded inserts embedded in rubber that pushed in from the outside and locked in place. Neat way to design mirror mounts.
Once I got the two mounting nuts out this is what I have left.
Using a template I made up from the GM mounting instructions I located the two end points for the mirror studs and the centre point for the access hole needed for the mirror adjusting head. The left hole will be clear, but the right hole is very near the original mirror mounting hole. The fibreglass is quite thick at this point – a good 1/4″. I won’t be able to use a hole saw to make the 1″ hole in the center as the original mirror hole is in the way.
I drilled the right hand hole just enough to accept the mirror stud so that I would have the maximum material between it and the original mirror hole . I then drilled the left hole the full 3/8″ as per the GM mounting details.Even so I then had to use a round file the take a bit of material from the left of the right hole and the right of the left hole. I expected to have to drill through a metal support under the fibreglass, but the support is further inside. The support has two holes through the inner support bar to access the sport mirror studs and one to take the mirror adjuster head.
I decided not to drill a 1″ hole in the centre. Instead I used the sport mirror plastic gasket to mark the opening in the centre for the adjuster head. Using a drill and an electric dremel with a circular filing bit to remove the material in the centre opening until I had just enough room to slip the head through the hole.
With the front window channel removed I had clear access to the two mirror studs. After tightening up the studs I ran the adjuster cable through the two holes in the front part of the door which is designed to keep the cable away from the window as it moves. There is an access door in the front of the inner door panel to help get the cable through the two holes. Here the cable head is in place to be fitted into the door panel which I will do later when all the work on the door is done and it’s time to replace the panel.
The online forums talking about installing sport mirrors at times claim it to be a real chore. This could be the case if the window and the front window channel are in place. With them out is is fairly straight forward. The most difficult part is getting the new stud holes in the right spot. For that I located the mid point between the two access holes on the inner support frame and used that to locate the centre of the template on the outside – that put the holes for the studs in the correct spot along the top of the door. The template also located the two stud holes in the proper location below the ridge on the top of the door. There is some wiggle room where the mirror sits along the top, but it is critical that the positioning from the top ridge is close so that the mirror sits level and is not tilting up or down.
Next: Odds and ends and checking over the window glass.