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XJ Flat Belly/ X member Build. Is it possible? Let's see....

50098 Views 76 Replies 21 Participants Last post by  DeftwillP
Well, thought I'd do a build on this separate from my XJ build. For those who don't know, my XJ is on about 3" of lift and 35's. I wheel my XJ in big pointy rocks that love to rip on anything they can on the bottom of my rig. I love the low stance of my heep and it works well, but it has it's drawbacks. EVERYTHING under my XJ has been taken into consideration because of it's low height. When you are this low, you rub and drag on rocks a lot. Is this a bad thing? Well, if you have the right armor and have clearanced everything that should be, then no. However, I have left one of the most important items untouched and it's way overdue for a replacement. This would obviously be my cross member. The factory X member is weak and hangs below the frame rails. At the same time, the bottom portion of the transfer case also hangs below the frame rails. This holds me up. Some how, I have yet to have exploded my transfer case. In the wheeling trips I have had this year, I have managed to turn the factory X member into an upside down U shape, which actually lifted my transfer case above the frame rails. Still, the cross member hangs too low. In this next pic, I was denied from getting to the top of this rock, even after repeatedly slamming into it trying to bounce and slide the cross member over the rock....

So, where does this leave me? It leaves me wanting a completely-flat -to-the-frame-rails-cross member, one that is strong, and wanting my transfer case completely out of the way. So first, out with the old....

To do this cross member, I got a clocking jig

and some 2x6 3/16 wall

So after doing some measuring, finding the center, and how much material should be shoved up between the frame rails, I came up with this....

Using the center point, I kinda (yes, kinda) figured where the trans mount should go. I drilled holes and got this....

And this is where I leave you hangin' til I get some more work done!
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Timo_90xj said:
What are you gonna do with the exhaust? Run a more compact- sized cat and muffler? It's pretty damn tight fight to get a muffler and cat tucked into a flat belly without cutting the floorboards.. :mad: Flat belly, low stance and large tires is the way to go IMO so you're on the right track :)

I'm guessing you don't even need to notch the tranny x-member for front DS with the clocked TC? How are you going to mount this thing, weld in an extra support plate to the "ears" and add vertical mounts with crush sleeves through the unibody? Sure looks like a good starting point :thumbsup:
The exhaust actually is going to work I think. My exhaust has already self clearanced itself into my floor board. If it is too tight, I'll massage the floor or notch the crossmember. As far as mounting, for the time being I'm going to use the stock mounting holes just to get it on there. As you can see, the metal sticks out long that the frame rails are. I'm going to fold that metal up around the frame to "hug" it and then run mounting points through the frame. I'm sure the bottom factory bolts won't last long!
I like that : ) .. while your there... should put some long arms on : )
Thanks. No long arms on this XJ. I can make short arms work just as well. I'll also have more clearance and making what I'd want (mid arm 3 link) is way more work than I want to put into it right now.
Nice work! Can't wait to see how your plan turns out, I've got to do something for mine.
Thanks dude!

You should rent that jig out when you're done. 5 bucks to your paypal and mail it to the next guy.

I've seen a thread where a reamer just travels around from one person to the next for people going to 1T TRE.

I've thought about clocking my t-case if I decide to pull it for my SYE, but 45 bucks for a jig I could make for myself seems spendy.

I have an old stock x-member that looks close to yours.
Is it legal to be a jig pimp? :rofl:

Should work that way..

If I may suggest, you might want to use 10mm countersunk hex-head bolts (class 10.9 or 12.9 so they are hard stuff), then weld another 3/16 plate to the bottom of the "ears" and drill large enough holes where the mounting bolts go through - so large that the head just goes through the hole as well.

This way you will have countersunk bolts, and the additional 3/16" plate both gives you added strength on the key area, and also gives you just that much clearance over the bolt heads so they don't get smashed to rocks as easily. I did the x-member on my ZJ this way, and I've scraped the heck out of it on rocks and so far zero marks on the bolt heads :thumbsup:
That sounds like a great idea! The studs in the frame, do they just twist out? I didn't want to try it to find out I couldn't put another bolt in there.
I'm sure you've seen these type of things before, but it's an alternative to the 3/8s plate idea. Plate would probably be cheaper anyway.
Actually, I have never seen those! Might actually order a few....

Yes the twist out, the double nut technique works very well.... wait, what? Also, if you look in front of the factory cross member mounts there is a sleeved hole on each side, you can tap that and use that for a 3rd bolt to hold the cross member on.
Thanks man. Good info. I'll replace those studs with new bolts.

I got a little more work done. I didn't get any pics but I will this week. I slotted holes for the factory mounting locations and all but got the X member completely under the XJ. I think I need to do a little more trimming on the middle boxed part.
I've been thinking about the idea of fabbing high clearance axle brackets, that way the lower arms would basically be flat up to around 3" of lift or so.. With a little extended wheelbase and adjustable arms that should work ok.

There are a couple issues though; you'd need to rebuild the upper mounts as well, basically needing to fab a truss (possible fitment issues at full bump). Another problem is the added leverage because of the mounts being fairly far behind axle centerline. Then again, with OTK steering and flat arms the on- road handling should be great, and axle articulation + obstacle climbing abilities when wheeling really good as well.

3- link mid arms or long arms would be great, but they sure are a lot of work.. but so would be high clearance brackets :D
I've thrown this idea around a good bit. I just can't justify putting that much work into a Dana 30!
Kinda thinking the same way :D Swap in a D44? ;)

I'd do that, if there weren't the stupid laws here in Finland that prevents me from deleting abs- brakes and running wider track axles..
I'm so stuck on the fence on this.I'm a college student so I don't make all kinds of money. I keep telling myself to stay on 35's until I'm done with school. If I did a 44 swap, I'd then want a 9" or 60 and 37's, do a mid arm 3link, blah blah blah......... :laugh:
Do you have the cash $$$ for 37 and a set of axles? Or to break stuff? If not stay on 35s
I'll stay on 35's until I'm done with school. I can afford 30 and 8.25 parts all day long. :laugh:
14b and it's parts are actually fairly cheap, but fitting under the XJ is another thing - and that's even more so with HP D60 fronts :D
The thing is, I have no desire to run over 37's/38's.
1990JEEPXJ said:
I will be watching this thread closely. Better not let me down
I won't dude! Hopefully I'll get a little work done between classes tomorrow.
Started back to school today but between classes I got some work done on the cross member. First off, it fits and all the bolt holes line up....

Then I cut some access slots to the trans mount bolts. No, they aren't perfectly square, but it's going to get thrashed on so who cares? I took one of the pieces of metal I cut out and welded it across the slots on the inside for a little added strength...

Here is a pic of the whole cross member...

So I slapped another stock cross member (not bent up one) on so I could get it out of the garage. Tightening up the bolts, one of the bolts just spins in the frame. Did I break a nutsert? What do I do with that?
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2 options IMO
1. Cut a hole in the side of the frame for new bolts. Not the best idea. It was done on my previous XJ.

2. Cut out both bolts(stud and nut), weld 2 nuts to a piece of 1/8 and weld in place of the old ones.
Thanks. I was hoping it would be something besides a pain in the d!ck. Sounds like fun :D
did you already drill out the holes on the trans? i wanna see how this is done. might do it myself but without the jig.
Not yet. I'll be doing this last.
did u use any wd-40 or pb or anti seize on the bolt? hand tools arent gonna be able to pull the bolt back out a quick zip with an impact may save u from a loose nutsert and a bolt stuck in it. Here at the shop with some fasteners u can get away with putting bolts with nuts in a bind and a quick hit with an impact will loosen it.

I your nutsert is shot which is very likely you dont have much options besides opening up the inside of ur frame to get a wrench on it or cutting it out from the bottom......
Like I said, this sounds fun. :D I'm pulling the stock cross member back off tomorrow to finish up the new one. I'll see what's up with it then....
Subscribed. This actually looks like a viable solution to not buying one. :thumbsup:
Yup, and you won't get a flat belly anyway else.
No pics, but I took Alex's advice, welded the nuts to the studs, and twisted them out. Also, I enlarged the slots to fit the bolts better. Hopefully, I finish this heavy bastard up this weekend....
Sack up and build a 44. Then wish you built a 60. Wanna buy a built 44?:rolleyes:
Hahahaha. 44/9" is something I'm always thinking about.

Bent the sides to "hug" the frame....

Bolted up...


Now I need to clock the case. I'll probably start on that Thursday. Also, I plan to build a transfer case skid and a trans skid off the x member very soon out of 2" square tube and 3/16" plate.
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alexrule123 said:
Looks good but my god how much does that thing weight!?
I don't want to know lol. But it's not as bad as I thought. My buddy had a flat skid in his TJ, which is basically just a big piece of plate and it weighs 60 pounds. I can't imagine mine being much more if not any more than that. I'm ditching the wet carpet so it will off set it lol. Plus, as long as I keep the heavy weight low, it doesn't bother me as bad...
Timo_90xj said:
At least all that weight is belowe your COG point, so it'll help keep the rubber side down :D

Looks good, but I'd worry a little about the mounting bolts below the frame.. I'd use countersunk bolts like I mentioned, I'm pretty damn sure you'll rip those off at some point.
Yeah, I don't trust those for hard wheeling. I'm going to run bolts through the sides of the frame too. Instead of counter sunk bolts, I think I'll get some of the bolt protectors from ballistic fab.
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