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Demco Hijacker Above-Bed Base Rail Kit Installation - 2017 GMC Sierra 2500

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How to Install the Demco Hijacker Above-Bed Base Rail Kit on a 2017 GMC Sierra 2500


Hey everybody, Ryan here at etrailer. Today on our 2017 GMC Sierra 2500, we're gonna be showing you how to install the Demco Premier Above-Bed Fifth Wheel Rail Installation Kit. But before we do that, let's check it out and make sure that this is something that's gonna work for you. So what this kit is gonna allow you to do is have a permanent hitch in here that's gonna allow you to drop in a fifth wheel head. And one of the cool things about this setup is it's gonna work with pretty much all those popular brands of fifth wheel heads. So you definitely have some choices there on what you can use.

Now, something I do wanna say, a lot of these trucks, I see a lot of them that have the short beds, the 6-1/2 foot bed. And that's exactly what we have here today. And our customer has a fifth wheel and he wants to be able to safely make those 90 degree returns and real sharp turns and things like that. Well, some of you may know, with the short bed that can cause some interference with the cab and things like that. So what he ended up going rip is an autoslide type head.

That way, when he goes to make those long turns, the head will slide back a little ways and give him that extra clearance. So just something to think about whenever you're choosing what type of head you want. And obviously, the rails are gonna be here to allow you to mount that head up. And the rails are custom fit to your truck, so for me, whenever I'm pulling a big heavy trailer down the road, it's nice to know that. It's nice to know that kit's designed to be paired up with this particular truck and not so universal that you kinda lose a little bit of faith in it.

So the fact that this bolts into the frame rails, definitely would give me a little more confidence. Just to take a closer look at the frame rails. So here's the plates and this part was super easy, actually. These plates literally just line up with some threaded weld nuts that are already in the frame, right from the factory and hardware just screws right in. So it's gonna utilize those factory attachment points and this side plate actually turned out really nice.

Back up top here in the bed, I'm just gonna grab a couple of measurements. And these are in regards to a lot of people who wanna know if they got some space to maybe put a tool box or an auxiliary fuel tank or something like that. And if you have a bedliner on this truck, so it will take up a little bit of space here. So just bear with me as far as that goes. But from the bolt head to the very edge of the rail here, that's gonna be right at about 24 inches. So got a couple of feet with there with the space. And if you're curious about the height, how high this has got to come up, maybe have a weird bedliner or something. I'll just measure from, we'll come where the channels are higher. And from that, it's gonna be right at about 1-1/4 inch. As far as the quality construction or how these are built, I would say they fall somewhere in the middle. They're not built badly by any means. I mean, everything is solid steel, has a thick powder coat finish on it. Something I'd feel confident using for sure. And just on a side note and for whatever reason, if you don't need the whole kit, let's say maybe you already have some rails from another truck or something like that, and you just need the frame plates, the side plates. What's cool is you can pick all that up separately and piece it together if you need to or maybe you lost a rail or damaged or something like that. You can always pick the rails up separately, as well as the frame plates or just grab the whole kit. Just to compare this kit to some of the other ones. I'd say it's right on par with a lot of them. I mean, they're fifth wheel rails, so not a whole lot to it. One of my favorite kits though, for any hitch, generally speaking as B&W. If you're familiar with the towing world, I'm sure you've heard of them. They make really high quality products as well. And actually our customer today originally had a B&W kit and a fifth wheel head and realized, I want that sliding feature. I want that hitch to have that on a slide and give me a little extra cab clearance. And that's why I ended up making the switch to the Demco here, which is definitely understandable. I get where he's coming from. And by doing that, his thought was, well, I just want to say brand specific here have the same brand fifth wheel rails as well as the head. That's something I definitely understand too. Will the other rails work Probably. I don't know, off the top of my head, but I get it keeping everything paired together. So this got him going in the right direction and hopefully it'll help you out too. As far as getting everything installed, it's really not terrible. Like the frame plates or the side plates, if you will. Those just bolt right on. So really straight forward there, even the rails in the bed, aren't too bad. You really wanna double, triple check your measurements and make sure everything's spot on. The hardest part by far is gonna be when you're underneath the truck here, just trying to get the hardware in from the rails into the side plates. Everything is really tight and it can be just tricky just to get everything lined up and actually started. And the hardest part is gonna be actually torquing that hardware down. Since you don't have the space, you can't just use a regular type socket. You don't have the room for it. So that's where things take a little bit of time. And I do when we're doing the installation, I'll give you a few different options on a couple of tools that you can use to make that little bit easier. So hopefully you'll have them laying around the house or a lot of times too, you can run up to the store and grab him them and if that's something you need to do. But speaking of that installation, why don't we go ahead and knock this out together now. To begin your installation, you're gonna be here up in the bed of the truck. And first thing you wanna do is clean out your bed and make it easy to work in here. If you have a drop in bedliner, I suggest removing that. That'll give us the most accurate installation and make it much, much easier. With that said, the first thing that you wanna do is take one of your rails and we're gonna have to find the placement of it. So you're going to measure from end of the bed, make sure you're going from the end of the bed and not the tailgate. And you're gonna take that measurement and make a mark. And then you wanna refer to the instructions for that correct measurement, because there is a difference between the short bed or I'm sorry, the 6-1/2 foot bed and the long bed. In our case, we have the shorter bed today. But what I do is make a mark and then I just use this as a straight edge to draw a line all the way across, and I'm gonna get it roughly in position. And then you wanna make sure that it is centered in the truck bed. So the way I do that is measure from our wheel well to the edge of the rail on each side. And you want that distance to be the same. So once I find that distance, I also use a straight edge and just make a mark there. That way we have a reference and we can make sure our rail is gonna be exactly where it needs to go. So since that line that we drew, the distance, they want you to line that up at the center of our rail here. And so you can look down through the openings and get it pretty close as eyeball it. But we wanna go and stop further and make sure it's exact and make sure that this is perfectly square. So what I've done is take your measure, go from the end of the bed again, and just go to one edge of the rail. In our case, I just followed this one. So for example, on ours here today, the edge here is about 32 inches. And so I made sure that the other side was at 32 inches and now we know it's exactly square. And once I found that, I just took our marker and traced all the way around it. That way we have a diagram or less on where this needs to go exactly. Now at this point, definitely need a couple of friends. You're gonna take your preassembled hitch, set the second rail up front, roughly in position. And then we're gonna take this and actually drop it into our rails. If they move around a little bit, not a huge deal. That's why we marked that one, exactly where it needs to go. So we can slide it around a little bit if need be. So once you have this in here, what you're gonna do, make sure this front rail is squared up and everything. What I've done is made sure the back was, where we originally had it, and then measure the distance between this edge and this edge and make sure that they're the same on each side, not a bad idea to check the distance from your wheel wells as well here. Once I found that perfect spot, again, I just drew a pattern around our front rail just to give us a reference. Make sure that we can constantly keep an eye on it while we're going through this process. From there, excuse me, each one of the rails, this hole, the second one end, that's the attachment points that we're gonna be using. So I'm just gonna take a marker, put a dot in the center. I already did the other three attachment points. And then what we're gonna do is I'm gonna drill a pilot hole. I just got a small, relatively small drill bit. And before we start doing this too, check underneath your truck, make sure you don't have anything that we're gonna drill into. You shouldn't, but if you have any aftermarket stuff down there, whatever, just to be on the safe side. Do your best here to get it in the center and we'll drill a small hole on each corner. Now we need to do is enlarge those holes that we drilled to 5/8 in diameter. Problem is even if you had that large or regular type drill bit, it's almost too big to go through this hole. And I really don't want to damage our square opening here in our rail. So since we have each hole pre-drill and marked already, what I think I'm gonna do is just move our hitch out of the way a little bit. This one looks like I was a little bit off. That's okay though. And if you move that out of the way, since we have everything marked already, we can use a step bit like this, or you can use your regular bit, whatever you're trying to do. With that said, I'll go ahead and enlarge all of our holes. Since this one, I am off just a hair. Probably just try to shift it over a little bit if I can. So what I've done is vacuumed up all over metal shavings and the holes that we drilled, I shot some spray paint over them and let them dry just to get a coat of paint over that bare metal, Slide the hitch back into the rough position and then you're gonna take these spacer blocks here, slide that in between the corrugation and then the rail. Then you're gonna take these hockey puck bushings, slide them in and line them up with the hole that we drill, like so. And then we're gonna take the long, I believe there's 3-1/2 inch carriage bolts, drop them down. We're gonna do that same thing on the three remaining corners. Now we can come over to our wheel wells and we're gonna be working on our frame rail. Wipe this down, get clean, and we're gonna be using four attachment points to bolt up our side plates. It's got two weld nuts here and two more weld nuts here. Not a bad idea if you spray them down with some penetrating oil, some type of cleaner and work those threads clean. I'm just using a tube brush. That way we can get some of that undercoating out of there. These GM trucks, I really pack on this undercoating and any dirt or junk out of there. And what we're gonna do is take our side plate. They are labeled, so you really can't mix that up. Driver's side. These slots up here, our bolts that we put in through the bed, those are gonna go through there. And line it on up, hold it in place. We're gonna take a bolt, a split lock washer, and get this started hand tight. What I like to do is just get one or two of them going. That way it will hold it roughly into position. And a lot of times what you're gonna need to do, every truck will be set up a little bit, a little bit different and how you drill them vary a little bit. So you may have to kind of manipulate this plate here to get the bolts to line up perfectly Looks like I might have to a little bit here. So what I'm gonna do is grab a tool. So I'm gonna use a tool like this, just spreads out a little bit. You can see right there. And one of those holes is blocked a little bit. I'm just gonna take this, put it up in one of those access holes and work that side plate over to hold the in position where I need it to be. And of course, once you have all of them started, we tighten it down and draw everything together, if that makes sense. So once we have these hand tight, we'll go ahead over to the other side and repeat the same process. Now we'd come back with a 15/16 socket and snug everything down. Now we need to make sure and come back with a torque wrench, tighten down all of our bolts to the amount specified in the instructions. If you don't have a torque wrench, you can grab one here at etrailer. Or a lot of times, if you go to your local auto parts stores, they'll have one there available to rent. So back up in the bed here, I went underneath our truck and just took a look at where we're gonna need to secure these actual bolts and upon further inspection, it seems to me we'd be better off taking the spacers that we had in here originally, and actually putting them underneath the truck on this part of the corrugation. It's one of those deals 'cause our bolt is literally going through the edge of our corrugation. So it could go really either way. If you put it here, this one it crush. If we put it here, one it crush. But I think what our best option is to pull these out since we don't have anything bolted down and you can just knock these out. We're gonna put these underneath. And you're also gonna have these large ones. I think we're gonna put these here, under there. And that way, if it does start to crush a little bit, this is gonna stop it and prevent that from happening. If it doesn't, not a big deal. We can always just slide these back out whenever we have everything tightened down. So I'm gonna go ahead and switch all these out and then go underneath the truck. So underneath our truck, you can see it here, our frame brackets and where our bolt comes down, take the spacer, slide this through like so. Now all these, they might not go in that easy and you might have to pry up on your bolt and slide the block and drop the bolt back down or pry this down a little bit. Every truck is just gonna be a little bit different. But once that's in, we're gonna take a flat washer, put that on up, and a flange nut. Get this going hand tight here and then repeat the same process for our three remaining corners there. So now we have all the bolts in there and hand tight. I came back with a regular box wrench and tighten them down as much as I could, which brings me to my next point. Now it's time to torque them down and you don't have a ton of space up there. So you can't get your classic socket on there. There's a few tools that you can use to make this a little bit easier. They're all gonna be 15/16 in size. One of them is like this. I believe this is called the dog bone if I'm not mistaken. This one worked out pretty well. It's relatively thin. The other one, you could use a crow's foot like this. And all these just go on the end of the torque wrench like that. So it's kinda low profile. And then there's another one. I assume this would be a crow's foot as well. It just doesn't have the extra sides, like a line wrench or something would. And fortunate, I have the right size in this one, but tightening a couple of bolts down already. One like this would probably work the best. So it's a lot more low profile and a little bit easier to get in there. But with that said, we can still make do here. And now that we know what tools you can use to get this process done, let's go ahead, we're gonna grab this one and I'll show you one of them getting torqued and how this works. So the way this works, it'll slide in there and go up and around the bolt. Obviously, before you torque everything, you wanna get them as tight as you can with a regular box wrench, try to draw everything down evenly. But once we have that done, we'll come back and make sure it's all torqued. As you can see, there's not a ton of room up here. So it's gonna take a little bit of time. Be patient with it. Take a break in between if you need to. It can get a little frustrating. With everything torqued down, what I did was remove our actual fifth wheel head. And in our case, we had this bedliner. So I dropped that in, kinda eyeballed it, kinda measured out where it's gonna hit our rails and I'm gonna just cut an opening out here. I'll lay it in there and make sure it fits and then I'll do the same thing for the rail up towards the front. So I'm just gonna use an air saw to do this. You can use a cutoff wheel, just whatever you have laying around. So I'll go ahead and get that done now. Well, got back cut out and dropped it on in and it's in there loosely, but it looks good, pretty happy with it. So what I'm gonna do is just measure the distance between our back rail to the front one. Take some rough measurements and then I'll probably just use a piece that we cut out here as a template. Saying just roughly measured, set this down, make our lines and come back and make our cut. And that'll finish up our look at and our installation of the Demco Premier Above-Bed Fifth Wheel Rail Installation Kit on our 2017 GMC Sierra 2500..


Info for this part was:

Employee Jeff D
Installed by:
Jeff D
Employee Joshua S
Video Edited:
Joshua S
Employee Jacob T
Video Edited:
Jacob T
Employee Chris R
Video Edited:
Chris R
Employee Dustin K
Video by:
Dustin K
Employee Zach D
Video by:
Zach D
Employee Michael B
Video by:
Michael B
Employee Aidan B
Video by:
Aidan B
Employee Shane H
Test Fit:
Shane H
Employee Robert C
Test Fit:
Robert C
Employee David F
Test Fit:
David F
Employee Ryan G
Test Fit:
Ryan G

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