Sport mirror mounting screws

[FL71C10]

Do sport mirrors use sheet metal screws to go through the backing plate? I bought a set of repop sport mirrors and was surprised that there were not threaded holes in the backing plate. It comes with sheet metal screws that go into the backing plate.

[Lee H]

No, was not a sheet metal screw. It is GM part number 9419728. It is a 14-20X7/8, stainless steel screw. GM used this fastener on many cars in many places in the 60s & 70's. They can be found on fleabay. The new old stock backing plate have the threads, the repops do not.

[gmc684x4]

Not my pic but does it look like this style
the stock ones on my 68 had threaded backing plates

Lmc does show there backing plate for this style are threaded


Not sure about the smaller mirrors i have seen on our trucks

Other way is to drill holes and tack nuts on your backing plates

[54blackhornet]

Just buy the proper screws and retap the backing plate to accept the screw.

[Ironangel]

Originally Posted by FL71C10

Do sport mirrors use sheet metal screws to go through the backing plate? I bought a set of repop sport mirrors and was surprised that there were not threaded holes in the backing plate. It comes with sheet metal screws that go into the backing plate.

That is correct, the 71-72 sport mirrors used three sheet metal screws that went from the outside in, through the mirror, the gasket, the outer door skin, and into the backing plate. I think the backing plates were glued in place when the mirrors were installed. Consequently over time the glue would fail and when the mirrors were removed the backing plate would fall to the bottom trapped inside the door. It's a good idea if you pre-drill the three holes in the door first. Use a 1/4" bit so the sheet metal screws will go through the door and bite into the backing plate. Use a little silicon or 5 minute epoxy to stick the backing in place inside the door skin aligned with the three 1/4" holes already drilled. I had a hell of a time trying to hold that backing plate while the sheet metal screws took hold. I finally ended up using 5 minute epoxy so I could start all three screws before torqueing them down. Use the backing plate for your template. The right hand mirror locates farther towards the rear of the truck door so the wing window pillar doesn't obstruct your view from the driver seat. Good luck!

[71CHEVYSHORTBED402]

Originally Posted by Lee H

No, was not a sheet metal screw. It is GM part number 9419728. It is a 14-20X7/8, stainless steel screw. GM used this fastener on many cars in many places in the 60s & 70's. They can be found on fleabay. The new old stock backing plate have the threads, the repops do not.

The screw type and plate depends. I believe the original plates had nuts, the GM replacements did not, though even some of their old mirror kits were set up for tap screws. Personally I like the nutted version much better.

Discovered those screws your showing had two different types of heads. Philips and I can't remember if it's a star or alan, but I'm pretty sure they take an alan wrench (Correction, Torx head). Otherwise they're the same screw, stainless steel. Guy I got them from thinks the phillips head came later. (Correction - Torx followed Philips) )

[gmc684x4]

My 68 truck stock mirrors are Philips head machine bolts like pictured
i would have to look as a young fella when the glass fell out off roading I took them off

looking into a hot rod build what was my original intention for the 68 low and fast broke young guy i was I got into 4x4ing and made her into a 4x4

[71CHEVYSHORTBED402]

Come to think of it, by the looks of the backing plate in post 2 there were at least two types of threaded nuts as well. Those are posts for lack of a better description, the nuts on my plates are square.

[Richard]

Have a pair of GM backing plates that look the ones in post 2 post by Lee H. I purchased around the year 2000 from a local dealer. Punched with a machine thread. They are GM, still have the labels on them. I think the original design had nuts welded on though. Have seen them. Purchased stainless torx screws to mount my mirrors. Torx would have never been used that far back. Aftermarket backing plates I have seen are punched for a sheet metal screw. Like the speed clips on dash, instrument panel etc.

[54blackhornet]

The backing plates where still attached to my 71 GMC even though the sport mirrors removed for West Coast JR’s. Both have captured nuts fitted to them. The plates are original equipment to vehicle.

[71CHEVYSHORTBED402]

Originally Posted by Richard

Have a pair of GM backing plates that look the ones in post 2 post by Lee H. I purchased around the year 2000 from a local dealer. Punched with a machine thread. They are GM, still have the labels on them. I think the original design had nuts welded on though. Have seen them. Purchased stainless torx screws to mount my mirrors. Torx would have never been used that far back. Aftermarket backing plates I have seen are punched for a sheet metal screw. Like the speed clips on dash, instrument panel etc.

Right, Torx head. And I agree, Torx followed Phillips. After another glance the part number succeeded the old one too.

And I agree, the original was a square nut welded on the plate, same style as the fixed nuts you find for body bolts.

I have (had?) NOS plates with the stickers still on for a tap screw. Part number 6263291-2. Found a website that shows three part numbers (two replacements), 6263291 is the later version (July 1972).

[FL71C10]

Here is a reply from GMC Paul's to my question:

Hi, John
All of the reproduction 1970-72 sport mirrors use the 3rd and final version of GM backing plate that was made that uses sheet metal screws instead of machine screws. There are still some NOS GM mirror backing plates floating around that uses the machine screws, but be aware there are also 2 different versions of these, the 1st version they welded a nut to mirror bracket or pressed it into place and tacked welded it also, the other version they pressed the metal hole opening slightly small and then made machine screw threads in the distorted raised metal from punching the hole. The 2nd version is known for having the bracket threads distort and strip out easily. So if you look to locate NOS mirror brackets I strongly suggest you get the captured / welded nut version. Hope this helps. Thanks for your interest and We Hope 2020 finds you Blessed with Health, Happiness & Prosperity and will continue to find you so!
My Best Regards
Sky @ GMCPauls

[DeadheadNM]

The NOS mirrors on my Blazer came w sheet metal screws and the instructions were dated 1971 - interestingly, the instructs were for a "G"series truck.

Here's an example photo of the screws (period NOS) I used and the (later run NOS) backing plates I used: https://67-72chevytrucks.com/vboard/...94&postcount=2

Either screws or bolts are probably correct

[Lee H]

Great information, thanks for posting GMCPaul’s response.

[57larry]

good info on mirrors, thanks

[71CHEVYSHORTBED402]

Sometimes we go pretty deep on stuff, it's pretty cool. Keep it up we'll be Mopar Nerds It's easy to understand why they like em.

I've been through a lot of cars, but only one Mopar, 75 Dart. Fun car I guess, only a 318. Sounded like a jet plane warming up. Ten minutes to warm up too, otherwise it would die on me. Without knowing much about them, if I could choose a car it would be a Mopar, the car in this picture would suit me fine.

Personally I'm so-so vintage Chevy passenger cars, much rather a Pontiac. It's just that vintage Chevy trucks are best