My drivers side mirror glass keeps sliding off the assembly. I tired to fix it a couple years ago with 3M trim adhesive. It held until this past summer then the glass started to droop again.

What should I use to fix this permanently?

 

100% clear silicone will stick it on for good.
Just tape in place till cured.

 

Thats what I had to do after some stupid cardinal kept pecking at himself in my mirror and knocked it loose!

 

if I grab a tube of Permatex #80050, that should work right?

 

cheaper to just grab a tube of 100% clear silicone in a caulk tube, $3 gets allot more.

 

Most glass places will glue those back in cheap. And it should stay better than silicone will ever hold. Urethane may work but it's pricey when all you need is a little.