Your GMC truck has a black, plastic cowl that covers the linkage arms on the wiper motor. The cowl serves as a barrier between these arms and potentially harmful debris. To service or replace the wiper motor, you must remove the cowl to access the motor's control arm, which connects to the linkage arms. You can remove the wiper motor cowl on your GMC truck right at home, using a Phillips screwdriver and a suitable socket wrench. If you have some experience as a home mechanic, the job should take about 15 minutes.
Insert the ignition key into the lock cylinder. Turn it forward into the accessory position, but don’t start your truck.
Turn on the power to your GMC truck's windshield wipers. When the wipers reach their highest point on the glass, turn the ignition key back into the off position. Remove the ignition key and exit the truck.
Mark the position of each of your truck's wiper blades on the windshield with a grease pencil. Without moving the wiper blades, trace around both of them as close to the blade itself as possible.
Follow the wiper blade on the passenger's side of the truck, down along the wiper arm to where it connects at the base of the windshield. At the wiper arm's connecting point, you will see that a five-inch long black cap covers it. Grab the cap at the base of the wiper arm, pull it up, then fold it to the side. The cap does not completely remove. It has a riveted joint that allows it to open like a door.
Remove the nut holding the passenger side wiper arm on its shaft, using a socket wrench. Grasp the wiper blade and wiper arm with both hands. Lift it away from the shaft that it mounts on, then set it safely to the side of your work area.
Lift the cap on the driver's side wiper arm just as you did on the passenger's side. Swivel the cap back out of your way and remove the nut holding the wiper arm in place with your socket wrench.
Lift the driver's side wiper blade and arm off its shaft just as you did previously on the passenger's side. Set the driver's side wiper arm down along with the other wiper arm.
Remove the eight Phillips screws that secure the cowl in place on your truck's frame. Four screws sit along the bottom of the cowl, and four screws sit along the top of the cowl. Place all eight of the screws in a safe location such as your pocket.
Lift the cowl at its center carefully because the windshield wiper fluid hose is connected to it. Pull the hose off the connecting tube on the cowl gently. Remove the cowl.
