GMC is a General Motors brand that is basically just Chevy products with GMC logos switch in. The GMC line of trucks (which are just Chevy Silverados) have the option of telescoping mirrors for added safety when towing. Telescoping side mirrors are support on dual swing arms that can be extended to see behind larger trailers. However these side mirrors can often be hit or damaged in crowded parking garages so they need to be repaired occasional.
Open the truck door that you want to remove the telescoping side mirror from. Locate the triangular piece of plastic that covers the area where the mirror attaches to the door. Use a flathead screwdriver as a pry bar and wedge the tip into the seam between the trim piece and the door frame. Gently work the flathead around the edge of the trim piece until it pops off. This exposes the retaining bolts and the wiring harness to the mirror.
Unplug the wiring harness from the bottom of the inside of the cavity. The plug is down beneath the lower edge so you may need to use the flathead to help it unplug. Then undo the three nuts on the retaining bolts with a socket wrench while supporting the mirror on the other side of the door. Pull the mirror off the door once the nuts are removed.
Pry the glass out of the mirror by placing the flathead underneath the edge. Push the glass up and the balljoint will disconnect from the rear. Pull the glass out and the wiring harness for the turn signal will come out as well. The glass of the mirror is glued onto the signal light backplate so you you want to remove it then you will need to slide a razor along the seam and carefully pry it out. The glass will likely shatter no matter how careful you are so do not take the glass apart unless you absolutely have to.
