Fifth Wheel Installation - 2012 GMC Sierra

Installation of a Fifth Wheel Hitch on a 2012 GMC Sierra

Today on our 2012 GMC Sierra Denali well be installing the 5th wheel hitch, part number RP30081 and the Reese base rail kit part number RP50066-58. Our first step will be installing the rear base rail. We need to measure from the end of the truck bed to the back edge of the rear base rail. Once we get our length, well then measure side to side to make sure were center of the bed.Now that weve got our base rail in position we need to go ahead and mark the holes. Im going to use a color paint pen so that it really stands out for me. Now with my holes marked out, Im going to go ahead and take an eight inch bit to make a pilot hole.

Now that weve got all four pilot holes drilled out, were going to get underneath the vehicle, were going to take our side brackets and temporarily set them in position and check to make sure our pilot holes line up with the side brackets.Now with our pilot holes lining up with our side brackets, were going to start drilling out our holes to the final size. Well be using the step bit process where in each drill bit will be a little bit larger than the one before. Our next step is to go ahead and install our side brackets ,but in order to do that we need to put some hard ware in the frame.Well be installing a 5/8 carriage bolt and block. To put these into the frame well need to take our bolt leader, our pole wire and feed it into our attachment point for this application, we actually have a closer access hole than going out to the end of the frame. Its located just behind the fuel tank.

So now well take our block, slide it onto our pull wire and then thread on our bolt.With the bolt in position we can now go ahead and take them and feed them into the access hole into the frame. Once into the frame well go ahead and just pull them into position. Youll want to make sure that your carriage bolt locks into your block. Ill go ahead and leave my pull wire on until I get my second attachment point in place. Then well slide our side bracket on, remove our pull wires and install the remaining fasteners.Now we can add a 5/8 serrated washer with the teeth of the washer facing the hitch and then a 5/8 nut.

Well just install each of these fasteners finger tight until we get all of our hardware into position. Now we have our side bracket mounted on the drivers side, well go ahead and repeat the same process on the passengers side.Our next step would be to drop our hardware down through the rear base rail into our side brackets. However, on the passengers side well need to remove the exhaust heat shield first. To give us a little working room were first going to remove the two rear tailpipe hangers. With our exhaust hanger lowered, we can now go ahead and cut the heat shield out.

Were going to cut just in front of the rear support beam and just behind the hat channel next to the fuel tank.With that done, we can go ahead and take our torch fit socket and remove the two support screws. As you can, see we have greater access to the passengers side attachment points for our base rail. Now well go ahead and get back in the bed of the vehicle and drop in our carriage bolts for the rear base rail. Before I put my bolts in position, Im going to go ahead and take the U-shaped spacers that are provided to take up the space between the bed corrugations.Well go ahead and set them above the side bracket but underneath the bed. This will ensure that when we tighten down our carriage bolt, that we dont smash the corrugation in the bed. Now that were back in the bed well go ahead and put our base rail into position and take our two inch carriage bolts provided with our install kit and drop them into place.Now well go ahead and get underneath, were going to add a conical tooth washer, lock washer and nut to all four carriage bolts with the teeth of the conical tooth washer facing up. Well install each fastener finger tight until we have all our fasteners in place. Now with the fifth wheel head unit bracket and legs pre-assembled, well put our front rail into position and then use the fifth wheel assembly to center it up. Quick tech tip; I like to also go ahead and take the hold down pins and put them in position to verify that the base rail is center of the truck bed and with the fifth wheel head unit.Now we can go ahead and mark out our holes and drill out for the front base rail, just as we did for the rear base rail. And just as we did for the rear base rail, well drill out for the front base rail and check it against our side brackets. Alright, now with our pilot holes checked out were ready to go ahead and drill out to our final size and then well drop in our carriage bolt.Alright, With our holes drilled out well go ahead and reinstall the front base rail. Just like we did on the rear base rail, well need to install the U-shaped spacers to take up the space for the bed corrugation. Now well go ahead and get underneath, were going to add a conical tooth washer, lock washer and nut to all four carriage bolts.Alright, now with all our fasteners in place, well go ahead and tighten them down. Now with the base rails tightened down, well go ahead and tighten down the side brackets. Now that weve got all of our fasteners tightened down well go ahead and torque to specifications as indicated in the instructions. Now were ready to go ahead and torque to specification on our side brackets.We have two more attachment points to drill out. These will be the center base rail attachment points, well drill out the closest to the cab for the front base rail and it will be the inside closest to the cab for the rear base rail. Well go ahead and drill them out using the step bit process just as we did before. Alright, with everything drilled out well go ahead and drop our carriage bolts in place.Now well go ahead and get underneath and install our fasteners. Well be using the same setup as we did for the outer fasteners, the U block, the conical tooth washer, the lock washer and nut. Now that we have all our fasteners in place well go ahead and tighten them down and then torque to specifications as indicated in the instructions.Alright, now with all of our fasteners in place and torqued to specifications, we can go ahead and reinstall the exhaust. And there you have it for the installation of our fifth wheel hitch part number RP30081 with the Reese base rail kit part number RP50066-58 on our 2012 GMC Sierra Denali.