GMC trucks are rugged, reliable, and have great styling. The GMC Sierra is the GM Silverado's sibling. They could be twins if the GMC truck didn't have a certain style of its own. Running boards are among the amenities you might find on a the Sierra. There are many styles to choose from but the installation is similar in every case.
Measure the distance from the front edge of the truck's rear wheel well to the front of the rocker panel where the running board will end at the front of the vehicle. Match the measurement to the actual running boards to be sure you have the correct length to install GMC running boards on your truck.
Locate the three mounting points where a GMC truck's running board mounting brackets are anchored to the vehicle. They are the rubber body mounts--each has a center bolt running through a rubber shock shaped like a donut and into the body of the truck. Install GMC running board mounts using the body mount as the anchor.
Take the front running board mounting bracket and secure it to the truck at the front body mount. Remove the center bolt of the body mount and replace it after including the front running board mount as an added bracket. Repeat the process for front, middle, and rear body mounts, add a running board mounting bracket.
Slide one bolt head down each groove on the underside of the running board for each mounting bracket coming out from underneath the truck. With the bolts in their grooves, you can fasten together the front of the running board with the front trim guard with the screws that hold it to the running board. Bring the running board to the vehicle and set the running board on top of the mounting brackets that reach out from under the truck.
Slide the bolts on the underside of the running board so that they line up with the holes on the mounting brackets. Slip one bolt through each hole and tighten a nut over each bolt to secure the running board to the mounting brackets. Use a ratchet wrench and an open end wrench to tighten these nuts and bolts securely.
Construct the rear of the running board. Cap the open end of the running board with the rear guard trim at the mud flap. Screw through the mud flap and body so that the screw penetrates through both the mud flap and the wheel well, into the running board base to create a rigid installation.
