bing tracking image

Curt Custom Fifth Wheel Kit Installation - 2020 GMC Sierra 2500

content loading

Customers compare C16429-204 to these similar products




Products Featured in this Video



How to Install the Curt Custom Fifth Wheel Kit on a 2020 GMC Sierra 2500


Hi there, GMC owners. Today, on your 2020 GMC Sierra 2500, we're gonna be taking a look at and showing you how to install CURT's above-bed base rail kit. And this is what our base rail assembly looks like when it's installed. We've gone ahead and slid in a fifth wheel in here, so you can see it attached. The rails will accommodate the majority of brands of fifth wheels out there. All the ones we carry here at etrailer should be applicable with these.

We are showing off a CURT here just to match with it. This is a slider, which is recommended for these short beds. So if you are putting base rails in your truck and you have a short bed, definitely check your cab clearance because this might be necessary for you. But with our base rails, they're fairly similar to a lot of the other manufacturers' base rails, such as Reese or B&W. You do get your base rails here on top, your mounting hardware to fasten it, and it is actually very similar to a lot of the other manufacturers as far as the type of hardware you use to secure it.

These are actually fairly nice rails. Comparing them to like B&W and Reese, they're very similar as far as the way they install, the way they're gonna operate. They do have a nice black textured finish on 'em, which looks really good in this particular truck. Me, personally, I prefer B&W over 'em just because the machining on the B&W is typically top notch and it's very consistent. So they just kinda fit a little bit better than some of the competitors.

But these rails worked out really nicely. They installed pretty easily. We really didn't have any issues with them. And they should work out fine for our customer here for getting this hooked up. Really, for this being more of an economical way to get base rails in your truck, this is probably the way I would go.

Because what you're getting for what you're paying for here, it's giving you everything that you need, and I really like 'em. Some of the other competitors like Demco, it's more of a little bit more of a premium option. I actually don't like their rails as much as these. These seem more low profile, so they're not gonna mess up your use of your bed as much as ones like Demco. They're gonna sit a little bit lower. All of our fasteners are here and not in the raised portion, so we don't have to worry about sliding things over it, causing big gouges into things. So, yeah, they're a really nice set of rails. If you're looking for, again, an economical option, you can also buy this as a kit with a fifth wheel so you can get that hooked up just like you see here in your truck. Now, you will wanna make sure you're using our fit guide to ensure that you get the appropriate base rail and custom-fit mounting kit with your setup. So that way, it'll perfectly install on your truck just like we did today. We'll begin our installation here in the back of the vehicle. Go ahead and grab your rear rail outta your kit. It looks the same as your front rail. You can't tell the difference so just grab one of the two. We're going to measure the distance that we're gonna set the rail in our bed. So the distance we're gonna measure is from the end of our truck box here, not the tailgate, the end of the truck box. And we're gonna be measuring out our distance where we're gonna be setting the rear edge here of our rear rail. Now, there are a couple of different measurements in your instructions based on the length of your truck bed, so you're gonna wanna make sure you're following the appropriate measurement for your truck, and go ahead and measure and mark that out. So I'm gonna go ahead and measure mine here. And I like to just put a mark here on the raised corrugation. It just makes it a little easier to see. And we're just gonna put a little mark right there. Come over to the other side and we'll do the same thing. All right, so we've got both of our marks made there. We can now bring our rail up, line it up with our marks. And then, we're gonna make sure that it's centered side to side. So you can use a kind of a visual cue here. The square hole here is gonna be the center of your rail. So I try to just visualize first, centering it here on the middle of this corrugation. That looks pretty close. Then, you can verify by measuring from the edge of your rail on one side to the edge of the truck and make sure that it's the same on each side. And we're still slightly needing to go this way. And we'll recheck. And that looks really good right there. So just double-check your marks, make sure you're on your marks. And once we've got that all set up, we're ready to start drilling. I recommend starting with an eighth-inch drill bit. So that way, we can just punch our hole, verify that it's in the right spot. 'Cause if you happen to get it in the wrong spot with an eighth-inch hole, you can just put a little bit of dab of silicone on there, and you'll never even notice that, that hole was there. So we'll start with that, double-check ourselves, and then we'll enlarge it as necessary. Once you've got it in place, I went ahead and marked each one in the center with a paint stick just to make it a little bit easier to see. But you can actually use your rail here as a template when you're going to drill these out. So I'm gonna grab my small bit here. We're gonna go right in the center, just drilling straight down through the hole. All right, and then after you've got it drilled, just go ahead and leave it like that. 'Cause we're gonna verify now that this is going to be the appropriate spot, and we can see our drill bit passing through the bottom so we can more easily verify that. So we're now on our wheel well on the driver's side. We just drilled down through this area. You can kinda fold this back to be able to see in there, but to make things easier, we're just gonna remove these fasteners and that'll let us be able to see in there a whole lot easier. It'll also make things easier when we go to put our side rail on. So we're gonna use a T15 Torx to remove these three fasteners here. And now, you should be able to kinda fold that back outta your way, giving you an opportunity to see in there a whole lot easier. So we can now see our drill bit poking down right there. So now, we're gonna set our side rail in place. And this is just temporary to make sure that everything's lining up. We want the two holes here to be towards the rear. A U bolt will attach to the side of the frame eventually and our single hole here towards the front. And that's what we're gonna be checking to make sure that our drill bit goes down through an attachment hole and that our other hole here lines up with the hole in the frame. So you can just kinda peel your liner back and slide this behind there. And then, we're setting it on top of the frame. Get it into position here. Okay. So once we get it roughly into position, we're checking to see here that our front hole lines up with this larger slotted hole there. That's gonna be our attachment point. So here, we can see our drill bit. We've got our bracket below it We're raising this up to where it's centered over our bit. And then, we're gonna raise up the front half and then press it into the frame here. What we're looking at is that our hole here at the front lines up with the hole in the side of the frame, which I'm just kinda sticking my thumb through there. And I can feel that when I stick my thumb through, that we are lined up with the hole. So now, that means that we are now okay to continue to drill. That hole lined up with the big one there. Our drill bit lined up with our slots there. So yeah, we're just ready to drill it on out. All right, so that all looked good when we did our alignment test. So I'm just gonna continue drilling out the rest of the holes. You'll wanna check this side the same way, make sure everything looks good over here. You're gonna drill out both of these third slot in, so one, two, three on each side. Drill both of those. Drill your center, one towards the rear. And then, one, two, three in on the opposite side, you're gonna drill both on each side of the rail there. Once you've got each of the pilot holes drilled out, you can go ahead and move your rail out of the way. And then, we're gonna enlarge them with a 9/16 drill bit. I did put a little paint stick on 'em just to make 'em easier to see because with the liner that's in here, an eighth-inch bit, once you move that rail outta the way, sometimes they can actually disappear on you a little bit. And you do just wanna be careful when you're drilling these. You don't wanna go through too far. There could be components below it that you could drill into, so you do wanna check below before drilling just to make sure and just verify. 'Cause some things you have plenty of space, but you don't wanna bring your bit all the way through or you may contact it. Now, we understand that a lot of you out there may not have a 9/16 bit. It's a pretty big size bit. Usually, you have to purchase it kinda separately. Most of your kits stop at like 3/8 or half inch when you go to buy a set of bits. So yeah, a step bit would also work fine if you wanna use that to enlarge it to the 9/16 size. So now, we just wanna clean up our mess here. We're just gonna vacuum up all the debris. And then, you can use some clear coat to paint your holes to prevent any rust corrosion from occurring. And we just wanna spray our hole here. That'll just help prevent rust to ensure a long-lasting installation. Now, with all the holes drilled out for our rear rail, we're gonna install our side plates. And in order to do that, it'll make your life a lot easier if you lower down your spare tire here. You get more room to work underneath, and it's gonna be necessary at a later step anyway to be able to access some of the hardware for the rails to be able to tighten 'em down. And we're just using a couple, you can use screw drivers. We're using little pry bars here to just hold the fender liner back out of our way. So now, we'll need to feed in our carriage bolt. So you're gonna get these fish wires that come in your kit here. Here is your carriage bolt that comes in your kit. It's a large one. Go ahead and slide it through the big spacer that comes in your kit. And then, thread it on to the coiled wire. Once we've got it threaded on there, we're gonna pass this into the frame. So kinda just work it in there, and it looks like it's actually not quite gonna fit. It's very close, but it's not quite. So we're gonna have to take just a little bit out of the frame there just to allow us to feed it in. So if your bolt doesn't quite fit, just grab a file and just a little tiny notch is all you're gonna need. You're not gonna need hardly anything at all. 'Cause the bolt is very close to fitting. It's just probably a little bit of just like the coating on it. 'Cause look at that, slides right in now. It just didn't even need much. So just knocking off just a little bit of that, and then we can slide this in here. So we're gonna drop the bolt in first. Then, you're gonna slide your spacer in. And then, we can kinda pull both of those back just like that. And now, we're gonna take our fish wire, and we're gonna feed that through the single hole that's here at the front of our bracket. So I'm gonna tip that up some, kinda rest it on the top of the frame. Slide my fish wire through the hole, and then, we can kinda, I like to get the bolt kinda started up already as I'm sliding this on just 'cause as the fish wire starts to uncoil, it can get caught in the bracket. And that makes it kinda difficult to get the fish wire removed. But we we're able to get it through there. Go ahead and remove your fish wire. Be careful not to push the bolt back into the frame. I'm kinda pushing downward on the bracket here to keep a pressure on it so it can't move. And we'll slide our flange nut on there. So we're now underneath the vehicle. We're just on the inside of the frame here. You can see our holes we had drilled out of our bracket. Obviously, it's gonna line up pretty well. The wiring here on the side of the frame, we're just gonna pop that out. There's a couple of little straps on in here. Just make sure that those get unclipped so you can pull this out some. And that'll be probably be plenty right there 'cause we just need it out enough to be able to get our U bolts in place here. And these are gonna slide up. We don't wanna pinch anything between them and the frame here. And then, if you look here at the bottom, I'm pushing the U bolt through one of the holes in the side plate. There's also a hole on top. It's gonna be a little difficult to see, but you wanna try and line it up with both of those. And if you're having a difficult time, you might need to loosen up your front bolt just a little bit if we went a little too tight. Because that hole's slotted there, and we can slide our bracket forward and backward just a little bit in this hole. And there we go. We we're able to get it around the frame. We're not pinching anything between it. And once it slides through the bracket, we're just gonna place our nuts on the other side. These are gonna be a smaller diameter nut than the one we use for the single bolt at the front. And we're just gonna thread these on here. And just like our front bolt, we're just gonna go hand-tight on these. I actually went a little bit too hand-tight on the first bolt, so we're probably gonna leave these even a little bit looser 'cause, again, we do need to be able to slide this bracket forward and backward just a little bit to get it to properly line up with everything. So that'll be good there. And we're gonna perform the exact same procedures over on the other side to get that side plate installed. It's gonna be exactly like this, just a mirror image because the single hole needs to be towards the front and it needs to go over the frame. Everything like that over on the other side. Now, before you go to install the passenger side, side plate, I would recommend getting this heat shield out of the way. You can work around it if you don't wanna take it out of there. But it's gonna make your life a lot more difficult when you go to torque your hardware and stuff at a later step. You will be able to reinstall it afterwards if you wanted to and stuff. So I just recommend getting it out of the way. You're gonna have a fastener here on this crosstube, one on the crosstube up there and two on the side of the frame. And you'll remove all of those with a 13-millimeter socket. And now, with all of our fasteners removed, we'll just pull this down and set it aside. I will say that I did test it when going to put my side plate on, and I did have to actually make a small notch out of it here in order to get the U bolts in place. So if you're planning on putting this back on, probably just trim this little section out of here so you can get it in there easily. So we're now back in the bed of our truck. We've placed our rail back in place, and we're just gonna drop our bolts down through. These are gonna be a smaller diameter than the ones we used to attach the side plate. We're gonna go ahead and secure it now. This is the middle attachment here. So we're gonna take these split spacers that you see here. Any point where it's in a raised part of the corrugation here, we wanna try to even that out with the lowered sections there. So we're gonna put on our spacer, then we're gonna take a spacer plate, put that into place, and then we'll secure it with one of the flange nuts. And then, when you're doing this, try not to push the bolts back up. So if you push it up and it's no longer in the square hole on the base plate, the bolts will wanna spin on you. So I'm putting a little bit of side pressure on the plates to help prevent it from pushing up. And then, we're gonna do pretty much the same thing here for our side plates. Slide in a spacer, sit on it, and then we're gonna place on another spacer underneath just like we did in the middle one. There we go. And then, we'll put a flange nut on the bottom of this. And same thing with this one, we're trying not to push it up. So trying to pull the spacer plate a little bit to prevent it from pushing upwards. And we're actually gonna snug this one down a little bit more just to make sure that it pulls it up some to make this one easier to install. And now, we'll slide our spacer into this side. And you might need to use like a small screwdriver or something to fish it down into place. Once you get that into position, you can put your other plate on and put on your other nut. We're gonna do the same thing over on the other side of the vehicle as well. Now, we're just gonna go back and just snug 'em up a little bit just to draw it down. We'll fully tighten these at a later point. So now, we're just here in the back. It's a good idea to just double-check. We snugged them down because we have to assemble our fifth wheel just a little bit to be able to use it to install our front rail. And I didn't want it to be too sloppy when we're trying to line this up, but you may have a little bit of play in each one of these bolts that can cause it to shift a little bit. So it's just a good idea to just double-check your measurements, make sure that you're still centered and at the correct distance. If you need to shimmy it just a little bit forward, backward, left, and right, just a hair, you can do so at this point. And we all look good here. So now that we've got our rails in place, before we drill, I do recommend just taking your tape measure and just making sure that everything is square. When you set your rail on there, it's gonna be really close, and you're gonna eyeball it and probably go, "That's good." But I do recommend just double-checking, making sure that your distance here that it's centered. 'Cause when I had just set it in here, it was really close, but we we're about a little over an eighth of an inch to one direction. So we just kinda scooted it over, make sure it's even side to side. And then, also make sure it's even from rail to rail. So I just measure from one edge of this rail to the other edge of the new rail. And do the same on each side to make sure those are the same as well to make sure everything's all squared up. Once you've got it all double-checked and squared, we're gonna go ahead and drill it out just like we did the rear rail. The only difference here is that instead of it being on this side for the center bolt, it's gonna be on the other side. So we're just gonna mark 'em and drill. We went ahead and double-checked to make sure these line up, everything looked good. So we're gonna drill these out just like we did the rear ones. I'm gonna switch to my step bit after I enlarge it here a little bit and bring it up to the same size. So now, we'll just take our bolts. We put our rail back in place. I did vacuum 'em up and put paint on it again to protect the holes. And our hardware's just gonna drop right down them now. We need to pretty much do a very similar thing to attach our hardware here. You can see here's our two bolts on the passenger side here. The side plate you can see here, our bolt dropped down through it. Above our side plate, we need to put one of these notched out washers, just like we did in the rear. So slide that into place. Might need a screw driver again to help you a little bit. And it slid around the bolt. Then on bottom, just like in the front, you're gonna get one of these plates here and thread on your flange nut. We're gonna do the same thing on the other side for this rear bolt here that goes through the side plate. The frontward bolt on our front base rail, we're gonna use a slightly different hardware on. Instead of using a washer that has a notch out of it, this one's just gonna have a hole in the center since there is nothing we really need to work around here. So that'll just slide up. That'll take the place of the space in the corrugation there to even things out. We can then slide on the next plate and secure with the flange nut. The hardware we used here for this front bolt here on the driver's side is gonna be the same on the passenger side as the driver's side for these front ones as well as the center bolts on your front base rail. So now that we've got all of our hardware loosely installed, we can now go back and snug and tighten everything down. We're gonna use a 15/16 socket for the large bolt that we fed through the side plate. And all the rest of the nuts for your hardware is gonna use a 3/4-inch socket. And then, we also went ahead underneath to make sure we snug all these bolts down as well. And you're likely gonna need deep wells, short wells, swivels, and extensions to be able to get to each of these bolts. And now, we're gonna go back and torque our hardware to the specifications outlined in our instructions. For these ones over your fuel tank, I'd recommend getting a tool that looks like this. It's a 3/4 on one side and it's got a size to fit onto your torque wrench on the other side. So it's a nice dog bone shape. You can also use crow's feet, which are similar, but they tend to spread open when you try to torque stuff with them. So these boxed-end ones work a little bit better. Once you get all your fifth wheel base rails fully tightened down and torqued, we can then just start reassembling pieces we took down like our heat shield, the fender liner bolts we took out, and we'll get our spare tire back up. And that completes our installation of CURT's above-bed base rail kit on our 2020 GMC Sierra 2500..


Info for this part was:

Employee Jeff D
Installed by:
Jeff D
Employee Jacob T
Video Edited:
Jacob T
Employee Dustin K
Video Edited:
Dustin K
Employee Chris R
Video Edited:
Chris R
Employee Jonathan Y
Video by:
Jonathan Y
Employee Schuyler H
Video by:
Schuyler H
Employee Conner L
Test Fit:
Conner L
Employee David F
Test Fit:
David F
Employee Jacob H
Test Fit:
Jacob H
Employee Ryan G
Test Fit:
Ryan G

At etrailer.com we provide the best information available about the products we sell. We take the quality of our information seriously so that you can get the right part the first time. Let us know if anything is missing or if you have any questions.