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Reese Quick-Install Fifth Wheel Base Rails Installation - 2015 GMC Sierra

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How to Install the Reese Quick-Install Fifth Wheel Base Rails on a 2015 GMC Sierra

Today on our 2015 GMC Sierra Denali 3500 we'll be taking a look at and installing the Reese Quick Install Custom Base Rails and Outboard Installation Kit for Fifth Wheel Trailer Hitches. Part number, RP56001-53. Here's what it'll look like once it's installed. Now, let's go ahead and put our fifth wheel into place to see how easy it goes in. This is going to be a super easy installation with the outboard design that ensures a simple access to the mounting points. It's got 10 bolt base rails and all the hardware included.

Extended length base rails allow you for mounting farther out on your truck's frame. It cuts down installation time by more than half, compared to universal kits. Compatible with Curt, Draw-Tite, Hidden Hitch, Husky, Reese, and Valley fifth wheel hitches. If your vehicle is equipped with plastic in their fender wheels, you'll need to remove these before you get started. To start our installation we'll go ahead and drop down our tailgate and grab our large frame rail. We'll put our rear rail into place in the back of the vehicle.

We'll need to get a few measurements from the back of the bed, that's going to be back here, to the edge of our rail. Keep in mind if your vehicle has a spray in bed liner that you'll need to make those adjustments for whatever thickness that bend liner is. We're going to take our tape measure and measure it out. Going to go from both sides, so we can get it square. Then we'll ensure that we have the same amount of gap on both sides and it's centered. Now that we've got our rail centered out and marked out where we want it, we're going to take our paint pen and mark the center of the outer holes on both sides.

This way we can pre-drill and drill out our holes. Now that we've got that done we'll go ahead and move our rear rail out of the way. We're now going to take an eighth inch drill bit and pre-drill our holes. Going to go ahead and repeat this same process on the other side. Now, once we've established where we want our holes and drilled out those pilot holes and verified that that's where we want them with that outside rail, we're going to go ahead and drill our holes out to our final dimension. Now's the time that we're going to fasten and secure our side brackets to the frame rail, so we pull this out and set it off to the side while we place in our spacer blocks and carriage bolts from the backside coming through the two holes for the hardware here.

Locate the access hole here at the front of the vehicle. Use the provided pole wire, placing the coiled end through the hardware hole and back out to your access hole. Once you have it out the access hole, we'll then place on their block, placing the coil through the block, sliding it in through the access hole, and then threading on our carriage bolt. Slide the carriage bolt into the frame. Then, pull it through to where it comes out the hardware hole. Go ahead and leave your pole wire attached at this time. That way in case if it falls back into the frame rail you can pull it back out. We'll take our next pole wire and put a slight bend in it. That way we can put it in the hole and bring it back out that access hole. Place your block and a carriage bolt. Push it down in and pull it out. Now, we're ready to go ahead and put in our slide plate. Take the pole wire, put it through your hardware hole on both sides, then we'll rotate it up in. You can also put up your bracket and push those back through, and then pull them through once you get it in place as well. That sometimes helps. You can let it rest there while we go ahead and grab our hardware. Now, you're going to take conical tooth washer and your nut, and place those on the end of both those bolts. Go ahead and remove that pole wire now. It helps to kind of hold it as well while you do so, so you don't press it back in. Now, we're not going to tighten these down until we get the upper brackets and rails inside the bed put in place. That way in case we need to make any adjustments or shift it back and forth, we're able to do so. Let's go ahead and go over to the other side and repeat that same process. Now, we'll go ahead and put our rear rail over the top of the holes that we drilled out and slide through our carriage holes. They should sit down completely flush all the way around, with the square of the carriage bolt locking into the rail. Now let's go underneath the bottom side. Now we'll go ahead and put in our spacers. They're going to go in between the corrugation and our side rail brackets, so that when you tighten them down, it doesn't collapse that corrugation in the bed. These will slide up in between and around our hardware. We have those in place. We'll then take our conical tooth washers and nuts and place them on the bottom end of our carriage bolts. Let's go do the same thing on the other side. Now, we'll go ahead and take our un-assembled fifth wheel arches and we'll set it into our rear bracket, so we can set our front bracket in place. Take the front bracket, slide it underneath, and drop it into place. Once you've done so, go ahead and center it up on the inside of the wheel wells here. Then, make sure that there's a little bit of room so it'll be easy to get it in and out. Now, we go ahead and mark the center of our holes the same as we did before, so we can pre-drill them out, and then drill them to their final size. Now, we'll go ahead and pre-drill out those holes over our marks. Always remember that when you're drilling holes through the bed of your truck that you're going to want to use caution that you don't hit any lines or tanks underneath. A good way to check yourself is, after you get those holes pre-drilled, just go ahead and take a small screwdriver, stick it through those holes, and ensure that it's coming out in the middle of the bracket where you want it. Now that we've verified that our holes are where we want them, we'll go ahead and drill them out to the final size. We'll go ahead and clear out any kind of debris away from our holes, so our bars and rails sit flush against the truck bed. Now, I'll go ahead and slide our front rails back into place, now that we've got it all cleaned up, and place our hardware through. Line up the holes. Slide them in. Again, they will sit flush and not be canted at all. Again, we'll take our spacer blocks and we'll put it in between our frame bracket and the corrugation in our bend around our hardware. We'll take our conical tooth washers with the teeth face towards the bracket, and our nuts, and thread them into place. Repeat that same process on the driver's side. Now, we'll go ahead and mark out our forward holes for the center towards the cab. Mark the center on both rails. Use that eighth inch drill bit to pre-drill. Then, drill them out to that final drill size. Now, we'll go ahead and tap these in and ensure they sit flat. Looks good. Now, we'll go ahead and grab our fifth wheel and put it into place. Now, if we go directly up from the center of the rear end we're going to find those two bolts. One directly above the tire and one located right here, just to the side of the fuel cell. We'll go ahead and place our conical tooth washer and nut on the bottom, since we won't need to use a spacer block, since it's up in the corrugation and we don't have another bracket that's going to be causing a gap. Here's your conical tooth washer hold to the bolt, and thread on your nut. We're going to move to the back one and secure it. Just about the spare tire, we'll have the other bolt. Going to place that conical tooth washer and nut in place, and finger tighten those down. We're now ready to go ahead and torque everything down to manufacturer specifications. Now, we'll go ahead and torque our top ones down first. Now, we'll go ahead and torque the ones in the center, underneath the bed of the truck. Now, we'll go ahead and torque the outer ones that connect to the frame. All right, now with everything tightened and torqued to manufacturer specifications, we'll go ahead and check and make sure that it comes in and out nice and smoothly. That will do it for our review and installation of the Reese quick install custom base rails and outboard installation kit for fifth wheel trailer hitches. Part number, RP56001-53 on our 2015 GMC Sierra Denali 3500.



Whats the measurement from rear of the bed to the rear rail ?

Etrailer Expert

Jon G.


According to the installation instructions for the Base Rail Kit # RP56001-53 the rearmost base rail needs to be 29" from the end of the bed (not including the tailgate) for a long bed or 24-1/4" for a short bed. If you go to the product page you can see the installation instructions and a diagram showing these measurements.

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