How to: Mount your XJ rear bumper inside the frame - JeepForum.com
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Unread 03-12-2011, 01:02 PM   #1
justanotherjpr
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How to: Mount your XJ rear bumper inside the frame

So, I've seen a lot of threads asking about this but nothing with more than 1-2 pictures and very little description.

My rear bumper is an AJ's offroad bumper. It was mounted with some 1.5"x2" angle iron that bolted to the bottom of the frame. It had some mounts that hooked with one bolt to the factory bumper bolts. This worked well enough, but the bumper flexed more than a few times and dented the corners of my hatch.

This probably wasn't a valid concern but I worried about pulling a heavy trailer with the relatively small attachment point - the potential to 'pull' the bumper free of the frame mounts or the tongue weight to 'push' it off the mounts or to bend them. I knew they flexed at least a little because the dents in my hatch.

I set out to cut off these mounts, open the frame, stick 2x4x3/16" in the frame and weld the bumper to those 2x4's. I drilled holes in the 2x4 using the factory holes as a template and welded nuts inside the 2x4's. I also installed HD offroad shackle relocation brackets at the same time.

The 2x4's ended up being right at 5 1/8" sticking out of the frame, and 16" into the frame - so ~21 1/8". The ends are cut at an angle because that was how I bought them and wanted to pick up as much as I could inside the frame. There isn't really room to go longer than 16" because the frame starts to turn in.

My mounts are as follows, from the bottom up. 1/4" steel (HD Offroad brackets) welded to the frame. The frame, 3/16" box 2x4 with nuts welded inside. I intend to drill holes through the side of the frame and weld more nuts inside the 2x4's to pick up additional attachment points. My math shows 18" of weld attachment for each 2x4 to the bumper. Up and down each side of the 2x4, across the bottom, and then up the sides 3" where it attaches to the underside of the top of the bumper. 2" across the top.

I was able to pick up the factory hitch bolts and another a few inches forward, so there are four per side instead of three like I had. I think the back of my Jeep would part with itself before this bumper would part from the 2x4's, and the 2x4's from the frame.

Now, for what you came to see! The pictures:


Bumper almost out of the frame:




Here is the back of the XJ with the bumper out. You can see that I cut the back of the frame open in this one


Passenger side frame hole:


You can see that I left the shackle bolts long. I drilled the 2x4's to match this bolt so the bumper would be easy to line up, and provide an additional semi-attachment. About 8" in the stock frame on the passenger side you will find a tab of 3/16" steel welded in. It spans the width and is about 1.5" deep. It's welded front and back and was difficult to chisel out. Some guys just cut this section out, some notch the bumper mount. YMMV.


Here's the obstacle on the driver's side. The gas tank filler tubes pass through the frame and are protected by this metal sleeve. I considered removing the sleeve and filler tube and cutting a hole for the gas tank filler tubes to pass through the bumper. It seemed way over kill so I notched the 2x4 instead.


Here's an overall of the mounts


The other side:


Profile:


Obligatory weld shot:
These welds were made by a friend using my Hobart Handler 140 with .030 flux core. No beveling before welding.


Here's a shot of the notch out in the driver's side 2x4.


Getting painted in my make shift paint booth:





When the paint dries I'll put it back on and get some of it mounted for you guys.

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Unread 03-12-2011, 01:10 PM   #2
cbordea
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good work, I especially love your window decal!
I also love your flag and am envious that you actually have insulation in your garage.
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Unread 03-12-2011, 08:45 PM   #3
justanotherjpr
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Thanks man
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Unread 03-13-2011, 12:47 AM   #4
96XJ0507
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Do you have pictures of the mounts that were on the bumper? I'm wondering as I ended up using 1/4" sheet bent into an L that is 2"x4" and still have time to change things.
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Unread 03-13-2011, 01:55 AM   #5
justanotherjpr
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Sorry, I don't have any with the bumper mount as the focus but you can see it here wedged between my frame and gas tank skid.

To be honest, I don't know if it was that big of an issue except because I came down really hard on this bumper a few times running over a car - I pretty much fell off the rear tires onto the bumper. Also, I've drug it over a LOT of rocks, and backed into the car we were running over more than a few times without being easy on the go pedal. However, if I ever do a different bumper, it will mount inside the frame with 2x4's. I see no reason to do it any other way on an XJ.







Edit: Here's a friend driving my XJ on the car in question.
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Unread 03-13-2011, 09:38 AM   #6
96XJ0507
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Ok, that explains it well, that is pretty light angle iron that they used.
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Unread 03-13-2011, 10:05 AM   #7
Diamond-x
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Great job documenting. This is what I want to do, as well as T/C armor, spare tire carrier, long arms.

Will it ever end?

Thanks for the pics of this
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Unread 03-13-2011, 10:14 AM   #8
2doorxj
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Looks beefy! Im going to have to do this to my JCR, the tie in brackets it comes with are dinky.
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Unread 03-13-2011, 10:21 AM   #9
BeepBeepGoJeep
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thats about all a neon is good for...lol.
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Unread 03-13-2011, 10:26 AM   #10
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nice wright up, been looking at aj's bumpers myself. lol nice pic
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Unread 03-13-2011, 12:31 PM   #11
justanotherjpr
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Thanks guys! No, it never ends does it.

The angle iron was 3/16" thick and was doubled up with an opposing 'L' at the bumper. I would not mount a bumper using angle under the frame when this is so easy to do and substantially stronger.

Edit: I would consider, however, turning the 2x4 angle on edge and sticking it inside the frame with weld nuts on it.

I was extremely disappointed when I saw JCR's 'Tie in' bracket. IMO that should be the mount not the additional support.

AJ's bumpers are great products. I really think the L that held my bumper on was an issue because of the extreme abuse it took. If I wanted to buy a bumper again, I would still buy AJ's offroad.
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Unread 03-13-2011, 02:10 PM   #12
leftlanetruckin
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Looks familiar....
Mine mid build....
bumperlegs.jpg
Finished:
bumper2web.jpg

I have 7 bolts per side, but I doubt you would need more than what you have

Martin
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Unread 03-13-2011, 02:23 PM   #13
justanotherjpr
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Looks great Martin! But remember, 4 of each side that go into the stock bumper bolts don't really count.
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Unread 03-13-2011, 02:30 PM   #14
leftlanetruckin
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Quote:
Originally Posted by justanotherjpr View Post
Looks great Martin! But remember, 4 of each side that go into the stock bumper bolts don't really count.
I bet there is more strength in one of the additional mounting points we have, than in all 4 of the OEM ones..
Scary to see tire carriers etc hanging off those OEM mounts huh?
Will have to hit you up next time I am out on I90 in Wa me thinks.....
Martin
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1998 XJ on 37's.JK Rubi axles with chromo shafts and ctm's, 4:1 transfer case, etc etc etc.The Cherylkee....
2003 Range Rover HSE, 4.4 Quad Cam.
1998 Range Rover 4.6 HSE
2000 4.7 4WD WJ with a rebuilt motor.
4.3/700r4/new frame buildup (YJ)....
http://www.jeepforum.com/forum/showthread.php?t=324622

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Unread 03-13-2011, 04:57 PM   #15
justanotherjpr
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Quote:
Originally Posted by leftlanetruckin View Post
I bet there is more strength in one of the additional mounting points we have, than in all 4 of the OEM ones..
Scary to see tire carriers etc hanging off those OEM mounts huh?
Will have to hit you up next time I am out on I90 in Wa me thinks.....
Martin
I would venture a guess that you're right about the mounting points.

Got my tank skid mounted up today and used anti sieze on the bolts. Broke one of my weldnuts so only 3 bolts on the passenger side - which I'm sure is enough.

Gave it the hi-lift test and did not seem to budge at all.

Let me know when you're in town. We'll get together at one of the burger joints. I'm sure we can find somewhere that's truck friendly.
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