4X4Labs Rear Bumper Build (1 Viewer)

[VagabondJesse]

I'm building a 4x4Labs rear bumper from their kit and figured I'd make a thread for it. I know there have been a couple of other good build threads for the 4x4Labs bumpers, namely this one for an 80-series where the process is very similar to the 100's after the frame crossmember is removed, and this one from a year ago. I referenced both of them extensively, but I also know that having more pictures and descriptions available can only help.

My truck is primarily the family adventure vehicle, and we usually go wheeling a couple of times a month when possible. I got tired of dragging my rear end coming off obstacles, especially when the truck is full of people and/or gear, so a couple of months back I was hoping to purchase a prebuilt rear bumper. However, all manufacturers were pretty backed up and it was going to be fall before I could get my hands on one. 4x4Labs' website said they were shipping kits to residential addresses in 2 weeks. I suppose I should have called them rather than just placing an order on their site though. It ended up being closer to 6 weeks and I had to ship to my employer's loading dock. Because the kit was still considerably cheaper than a prebuilt bumper, I went ahead and ordered a front bumper kit, too. The clearance will be nice, and having a winch will be good peace of mind. ...for the Jeeps sharing the trail, that is!

Here's a rear bumper kit with dual swingouts (spare carrier and ladder), along with a front bumper kit as it fits in the truck:

Here's how she looks a couple of days before any of the work:

This is at my maximum departure angle. The hitch is slightly digging into the dirt as this photo was taken at Bill Moore Lake near Empire, CO:

A look from behind with the spare removed. You can see I've mangled the trailer wiring connector on a few obstacles:

First thing to do is remove the factory hitch, rear bumper cover, step plate, and spare tire winch. Then cut off the resonator:

 

[VagabondJesse]

Leaving a view like this:

Then take a deep breath and cut off that rear crossmember. Sawzall is definitely the way to go here. Maybe with a big (8"+) grinder in second place.

Then clean up this where you cut so it's all nice and flush. Here's a before shot. I don't have a good 'after'.

Now we get to the fun part- fitting, tacking, and welding. The main bumper structure is essentially 5 parts- 2 pieces that bolt to the inside of your frame rails (1 per side) that you can't see once everything is done, a big bent plate per side that mounts to the bottom of the frame rails (where the hitch was, if you had one like mine) and extends up the side of the vehicle, and then the main rear piece that extends the width of the vehicle.

I loosely attached the pieces to the inside of the frame rails, and then bolted the outside plates tightly. I didn't worry about their alignment yet. I then aligned the inside pieces so the bottoms sat just on top of the side plates and tightened them to the frame. Then loosened the side plates and aligned them where I wanted them on the side of the vehicle. It was at this point I placed the main bumper piece in place and centered it, loosening and adjusting the side plates as needed until everything was aligned where I wanted it, based mostly on the lines of the truck's body. The edges of the pieces also lined up fairly well, with the exception of this spot on the corner, which has a gap no matter how I positioned things:

Once things are in place where you want them, it's time to fire up the welder!

 

[atnolan94]

I just built my labs rear in the spring. Had to have them ship out a few odds and ends. My biggest issue was the spindles they sent me were cut entirely too short. They sent me some new ones and it was good to go. I also decided their jerry can carrier sucked. I had adapted a C4 fab carrier to my previous dobinsons bumper and enjoyed it so I threw another on this pumper using their accessory "saddle" and pieces of their carrier. Very happy with it.

 

[VagabondJesse]

When I was 18 I had a job installing loading dock equipment where I did a lot of stick welding. I never really learned how to weld properly though. It was a situation where the welder was already set to the current that we used, we only used one type of rod (didn't know what kind at the time), and pretty much everything was 3/16" mild steel. I welded a few different types of joints in a few different positions and directions which required different techniques, but my skills were rather limited.

I didn't realize that until I started this bumper. It's been a long time since I was 18. The little skill I developed is long gone, and I learned mighty quickly that different electrodes behave very differently. I now believe everything I did when I was a kid was probably with 6013, and I've used 6011, 7018, and 6013 for this project. All of my 7018 beads looked like crap, and all but the very last 6011 bead was just as bad. When I switched to 6013 everything magically turned out great! Luckily I did all of the hidden welds with the 6011 and 7018, and most of the visible welds are with 6013. I'll be grinding all the visible ones for aesthetic reasons, and nearly all of them have some awful looking welds on the other side of the joint, so I don't have concerns about the structural integrity. This is a very stout bumper.

Oh, and I had it in my head that I would have the patience to TIG weld this whole bumper, since I've had a fair amount of practice at that in the past couple of years. Granted, most of that was on stainless, and on rather small stuff around my home brewery. I did about 6 inches of TIG before I realized that it would take me weeks longer than I had planned. That was when I grabbed some stick electrodes and decided to refresh my muscle memory. Anyways, back to the bumper at hand.

With the basic shell in place, I made sure all of the mounting bolts were tight and then tacked everything.

I thought the next step was to take the bumper off and then finish weld everything. It turned out the next step was to drive to Harbor Freight and pick up a hydraulic table so that I'd be able to move forward without another set of hands. The cruiser is the only vehicle I had big enough to bring the hydraulic table home, so I drove there with the tacked-together bumper on. Luckily it's less than 2 miles down the road. Back at home I welded all the joints I could reach. If you know what you're doing, the gap at the corner of the bumper shouldn't be too hard to fill. If you're me this past weekend, it's a bit of a pain.

Then grab a beer and wait for the bumper to cool before installing it back on the vehicle to make sure it all fits, welds aren't getting in the way, and nothing deformed so much as to make reinstallation difficult or impossible. Luckily I didn't have any problems here. Remove the bumper again and we'll add the receiver, towing crossmember, receiver gussets, and recovery points. The crossmember will likely need to be cut to length. Do this, then tack in place on the top edge, somewhere that will not interfere with sliding the recovery points flush to the crossmember. You can tack the recovery points in place next. The bumper is upside-down in this photo:

Then you can slide the receiver tube in place. It will sit flush up to the towing crossmember, but because it's a bigger tube than the crossmember, you won't be welding all four sides of it because the bottom face will sit about 1/4" below the crossmember. The gussets can be tacked in place at this point. I welded mine flush with the edge of the crossmember so they're as low as possible. My thought was that will make it easier to attach safety chains when towing.

Then it's a matter of finish welding everything to this point. And in my case grinding. If you're a better welder you can probably just chip off slag and move on to the swing-out spindles. I'm halfway through grinding and cleaning up, so I'll add more once I move further.

 

[clrussell]

Watching. I’ll probably end up with one

 

[atnolan94]

Oy, head to HF and pick up a titanium brand mig welder. 10x easier!!!

 

[xplore]

Very nice! I already have a steel rear bumper, but not as nice as that one. Mine didn't negate the frame cross member, so the integrated hitch mount is lower than I'd like it. I think I'm going to take mine to a fab shop and have it modified, but I'm loving that design. If I pick up another 100 series in the future, that'll be the bumper for me.

 

[2020 Rocks]

I just finished building the same bumper a week ago, was under the gun with an upcoming camping trip and did not do a thread. Nice job! The only thing I changed up with the build was adding some corner gussets behind the cross member as well.

 

[VagabondJesse]

The only thing I changed up with the build was adding some corner gussets behind the cross member as well.

Ah, I like that idea! I've got some steel plate laying around, I may do the same. The only modification I had planned was to add a 7- and 4-pin trailer connector into the bumper. Picked up a Hopkins 40974 that I think can be made to work.

Something I hadn't thought about yet- where did you mount your license plate?

 

[2020 Rocks]

Ah, I like that idea! I've got some steel plate laying around, I may do the same. The only modification I had planned was to add a 7- and 4-pin trailer connector into the bumper. Picked up a Hopkins 40974 that I think can be made to work.

Something I hadn't thought about yet- where did you mount your license plate?

I bought the double swing outs but none of the accessories. I still need to work out how I want to setup those things, so for now the license plate hasn’t moved.

 

[DTCsk8er]

Just towed a 4.8k trailer with my 4x4labs rear bumper i built a few years ago; not a single issue at all. Be confident in your welds before you tow anything obviously!

I'm pretty damn happy with my bumpers.. other than the rattling the rear makes, which is not really even bothersome if the music is on.

 

[VagabondJesse]

Do you know what part of the rear rattles? Maybe there's something I can do during fab to help reduce it?

 

[DTCsk8er]

Do you know what part of the rear rattles? Maybe there's something I can do during fab to help reduce it?

Pretty sure it's the arm with he tire on it.. because the stop tab is riding on the bumper she'll surface when closed, any vibration on that arm makes a rattle/squeak.. you can really hear it with the windows down and wheeling..

 

[changingground]

Do you know what part of the rear rattles? Maybe there's something I can do during fab to help reduce it?

Jesse- I’m finishing up my tire carrier (soon) and would be happy to help you suss this out. Since I have yet to hang a tire off the back of the bumper I haven’t personally experienced the rattle, but I’m sure it’ll crop up!

 

[squheim72]

Mine rattles like crazy. The only thing pressing the arms to the bumper are the hydrolic shocks to keep them from banging. I’ve had to use felt pads that go onto the bottom of dining room chairs to muffle the sound. No matter how tight I make the latch, it bangs and rattles. Just my $.02. When you install the mounting points for the shocks, I would suggest you make them as offset as possible.

 

[atnolan94]

Mine rattles like crazy. The only thing pressing the arms to the bumper are the hydrolic shocks to keep them from banging. I’ve had to use felt pads that go onto the bottom of dining room chairs to muffle the sound. No matter how tight I make the latch, it bangs and rattles. Just my $.02. When you install the mounting points for the shocks, I would suggest you make them as offset as possible.

This is a good suggestion. I offset mine as far as I could and the cam action is extremely strong. The latch on these is just ok. The latches on my dobinsons bumper were a little more complicated but way less prone to rattling and movement.

 

[Choo Magoo]

I just finished mine up a few months ago. I can confirm that the tire carrier does rattle something fierce, especially on corrugated roads. Even with all the gusseting I did in my experience the problem can be solved by having 3 points of contact, triangulation if you will. So one point would be the spindle, one would be the latch, and in my case the third is a pickup truck latch mounted just under the rear window (not pictured). They are rock solid now and I no longer fear stress cracking at the welds of the tire carrier from a 150 pound tire rattling away up there. I also tried a second latch to clamp the arms back into the stops but that didn't help much either.

 

[TrillyPop]

My license plate is mounted to the underside of the jerry can holder.

As far as rattling goes - also have had that problem. It's just the design of the single latch for both swingouts. Used the soft side of velcro and also some weather stripping...both work but would get smushed down after a short while and rattling returns. A more long term solution I have found that works is to use the highest grade thin 3M automotive tape and some very thin ABS plastic onto the little tab where the swingouts contact. It helps to make the latch really snug and haven't had a problem with it coming off for a long time now. It's definitely requires a generous tug to unlatch and a kick with the foot to latch, but nothing moves or rattles. Can post pics if requested.

 

[squheim72]

I saw an 80 series 4X4 Labs bumper that had something that I don’t know how to explain. It had a concaved dome piece under where the end of the arms meet. The tabs on the bottom of the arms that push against the stop slid over the concave piece and it helped hold the arms in place. I wish I had a picture. Would like to try the same with mine to decrease the rattle.

 

[DTCsk8er]

My license plate is mounted to the underside of the jerry can holder.

As far as rattling goes - also have had that problem. It's just the design of the single latch for both swingouts. Used the soft side of velcro and also some weather stripping...both work but would get smushed down after a short while and rattling returns. A more long term solution I have found that works is to use the highest grade thin 3M automotive tape and some very thin ABS plastic onto the little tab where the swingouts contact. It helps to make the latch really snug and haven't had a problem with it coming off for a long time now. It's definitely requires a generous tug to unlatch and a kick with the foot to latch, but nothing moves or rattles. Can post pics if requested.

If you don't mind, I'd like to see a photo!