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As I get ready to build the new ZJ, strengthening the unibody is one of my major areas of focus, and one of the major reasons I need to build another one. I've gotten 15 years out of my current unibody, and given what I've done to it on and off the trail, I'd actually say I'm satisfied with it. There are a couple issues I'd like to prevent on the new rig though. I'd like to avoid lambo doors, prevent the unibody cracking around the d-pillar/unibody rail/rear x-member junction, and just in general make it more secure. But I don't want to make it a heavy pig either. One other spot I'm having issues, is the unibody is actually crumpling up against my rear Clayton's mounts, kinda weird, and not sure what actually caused it.
Current plans are to put new Clayton's brackets on, and boatsides tied in to the unibody stiffeners on Clayton's kit. I had also planned on putting a cage in/on that would resemble what Ryan did on Trucks! back in the day. I can't do a full interior cage, simply not enough room. But I wanted a roof halo outside, a-pillars outside. A hoop/x on the b pillar that goes through the roof and ties to the roof halo. With the seats as far back as I put them, I don't think I'll need much on the c-pillar, and then the d-pillar could go either outside or inside, I think inside would look better, outside would be easier.
How much of that is actually needed though? I know nobody (except maybe Chad) rolls their rig on purpose, but in 15 years of wheeling I haven't even come close. And I'm not building this rig to do trails harder than I've been doing, I'm building it to do the trails I'm already doing more comfortably and reliably.
I have no problem with building the cage, but if I can save the time and money needed to do it that wouldn't be a bad thing.
Not exactly an answer to your question, but are you planning to reinforce the unibody beyond the Clayton's stiffeners? IIRC, the Clayton's setup doesn't run the full length of the unibody. I would think the more rigidity you can add to the unibody the better, in particular I would think that torsional rigidity would really help to keep the doors & liftgate from getting all jacked up.
I'll probably plate some of the rails, or I could use the same style that Clayton does along the bottom of the rails. I remember Kraqa modeled that a while back and found it stronger than fully sleeving.
Dave, when I built my long arms I had pieces bent to sleeve the unibody rails from the front bend to the back bend, pretty much from the stock LCA mounts on both ends. I did that to spread the stresses of the control arms over a much larger area in hopes of eliminating any tearing of control arm mounts from the unibody. It also made a great place to weld the rear uppers to. I'm running radius arms in the front. When the sleeves were bent, the guy that did it for me also CNC cut holes along all 3 sides so we could plug weld it to the unibody. Also re-did the skid plate mounting. If you want to take a look I could bring it by sometime if it's a route you want to take.
Ken, Clayton's uses a similar system, but doesn't go quite as far as yours. But it does connect the front and rear LCA mounts for the long arms. Most of my unibody issues have been outside of that area though.
Your issues have been outside of the Clayton's brackets or outside of the flat/straight part of the Unibody My sleeves are wheel well to wheel well in length.
Ah, ok I get it now. Are you thinking of plating the back and tying the two sides together to eliminate the potential for twisting? A hitch or bumper would do a nice job for that. Or do you think the rear cracks could have been a by-product of having the top chopped for a couple of years? Maybe attaching the halo via the d-pillar to the Unibody will solve some of that too. But then you're starting to add more weight.
I could see in bending as you're essentially adding a stiffening rib, but in torsion I think fully boxing/sleeving would be stronger and IMO that's what ZJs really lack is torsional rigidity.
Agree on tying the unibody together somehow in the rear. I don't think a hitch by itself would be enough, but maybe if you sleeved the unibody, had a stiff rear bumper and/or tied them together with cage work it would be stiff enough to resist twisting.
Here's a link to our ZJ frame stiffener kit on ebay (the pics on our website dbmetalworx.com needs resized). It's made of 10 ga steel, and goes full length front to rear. The center section fully encapsulates most of the frame rail. Plating the uniframe then doing a 2x4 or 2x6 inch rocker replacement, then tying the rocker to stiffeners, makes a very sturdy foundation to mount a cage.
http://www.ebay.com/itm/Jeep-Grand-C...e=STRK:MESE:IT
Subscribing. Headed this direction on mine this winter.
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I have started my cage build. It turns out both B-Pillars and both C-Pillars are twisted and there are cracks in the metal. I'm planning on doing more to keep the pillars in place and functional doors.
With a hitch, factory gas tank armor, and rear steel bumper (using the bumper bolts) the rear end is incredibly solid. I can jack or jump on the corner of the bumper and there seems to be no discernible twist. The load paths are going through the steel not the uni-body. Now with a 3/16" closed triangular tube (4" x 7" x 8") as the rocker replacement, jacking the vehicle causes no discernible distortion. This leaves the front. Nothing ties the rocker rails into the frame, or across. Boxing the rockers is definitely a easy low cost alternative, alone with a box for a rear bumper.
Cut out rockers with frame tie insurance help the pillar twisting alot. Might want to consider that instead of bolt on sliders.
My next project on the ZJ is a cage. i'm OCD and dont want to see the cage.
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