If the window of your 1999 GMC Sierra is damaged, it is important to replace it as soon as possible. The window installation process is fairly long and complex, but it is straightforward. Experienced mechanics can replace a Sierra's window in about half an hour, but novices can expect to take well over an hour. Accessing the window requires a Phillips screwdriver and a socket wrench in order to remove the bolts and screws holding the door together.
Open the driver's-side door and lower the passenger window. Remove the interior door trim. The door trim is held in place by several screws along the edge of the trim. Once the screws are removed with a Phillips screwdriver, you can pry the trim off the door with a flat-head screwdriver. Be sure to unplug all of the electrical-wire connectors that are attached to the trim before removing the door trim.
Remove the two bolts holding the inner-mounting panel to the door with a socket wrench. Once the bolts are removed, pull the inner-mounting panel off the door. Pry out the four clips securing the speaker to the door and remove the speaker from the vehicle.
Remove the bolts securing the power regulator to the door with a socket wrench. Pull the power regulator off the door. All that should be left on the door is the window itself and the front roller. Slide the window until it is off the front roller and onto the securing notch at the edge of the door. Remove the front roller. At this point, you can remove the window by pulling it up and out of the door.
Install the new window by placing it onto the securing notch of the door. Reattach the front roller, snapping it into place below the window. Slide the window back onto the front roller. Reattach the window regulator and install the securing bolts. Reattach the speaker and the inner-mounting panel. Reconnect all the electrical-wire connectors and reinstall the interior door trim.
