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5.3 powered, full framed XJ on BJ60 axles


NAXJA Forum User
Vancouver, BC
Hey guys. Been a while since I've been on here. Just not much left for Jeep questions as my little XJ has been doing whatever I point it at. Current setup is a 98 XJ, 5.3L/4l65e/hybrid np231/241 c/j on "built" 30/44 and 35's. It's fully plated and braced to the tune of around 5000lbs and as it sits, I couldn't imagine wanting more out of it for what I've been doing.
This is going to be a little bit of a long history. If you're confused or angered by a few paragraphs, run.

BUT, I've been pushing it harder and stupider and have run into it's limits.
1. 35's just aren't quite enough anymore. I keep up with the guys on 40's all day, but doing so takes its toll pretty quickly. Need to go bigger.
2. While the Unibody will hold up to anything I throw at it, it won't hold up to being flopped. My concern is that the amount of work I've put into making the uni survive, probably accounts for 80% of my time/work. ie: Full plating, bracing, tubbing wells, fitting the v8. If/when I flop or roll, all of that work is 100% sent to the recyclers. All I really get to keep is the drivetrain and my shitty axles.
3. Because of the weight I've added in plating, a cage is out of the question. I'd be 5500 lbs by the time it's fully caged, and even then, there's the very likely possibility that a stray root or branch hooks part of the body that can't easily be replaced, and then I'm a heat score just begging for a VI notice (vehicle inspection). Cops are getting absolutely silly about VI's lately, and there's no way to fight it, nor any arbitration process. You get a VI here in BC, you don't waste money trying to pass even if your rig is 100% legal. You throw it out and start again.

The those reasons, I started thinking about possible solutions. The problems I need to solve are:
1. Need bigger axles that'll hold up to 40's.
2. Superstructure needs to survive 40's on buggy trails.
3. Needs to be able to carry the same amount of gear as my XJ, safely, without it all being on the roof.
4. Needs to have an easy/cheap to replace body.
5. A cage is probably a good idea.
6. It needs to run the same engine/trans as I'm running now. I can't go any smaller than 325hp.

So with those requirements in mind, I started looking at my options. I decided that I needed a full framed vehicle but that I wanted to keep the final weight below 5000lbs (ideally no more than 4500). I ended up picking up an 85 4runner for the frame, throwing another 5.3/4l60e/np241 onto it, and built some hybrid BJ60 axles (those are essentially the 1ton of the toyota world) with center rear and DD front. This was seeming like a fantastic plan until I discovered that first gen runner bodies in clean condition are as plentiful and cheap as gold plated unicorns. Sorta depressing as I do like the body style, and the truck is already driving at this point (around the yard). The frame rails are a little skinny up front so I was planning on chopping them out and rebuilding them a bit wider so I can drop the motor even lower and maybe even back another few inches. As it sits, the center of gravity in this truck is probably 3" lower than my XJ, despite being on 40's.


So anyhow, here's where I'm at now. I've been considering finding a cheap XJ shell, chopping the uni-rail out and tossing it on the frame. The XJ is slightly shorter, very low profile, has taller windows so I'm not smashing my meat-brain every time I need to stick my head out the window, etc. They're usually easy to find, but for some reason, there's nothing available right now.

But, to the propper fabbers out there, I'm looking for input.

1. How best to attach an XJ shell to a frame. I can modify the frame to fit the contours of the XJ underbody, but the XJ really doesn't have any solid spots to attach to the frame. The floors are notoriously flimsy. Should I just weld in some 1/4" x 8x8" plates every few feet and run some big bolts through? Think that'd hold, without thrashing the unibody?

2. Once I've got a frame, I still want to be able to both cage the body as well as keep it relatively easy to remove so I can get the shell out for replacement. I want to be able to keep the shell as stock as possible to save on work. I'd have to tub out the rears and chop the fronts, and maybe bob the back a little, but thats about the max I want to do. To properly triangulate a cage, I know I should be doing something behind the front seats. I was thinking I could just put one of the body mounts behind the front seats and have some tubes bolt in there, to the opposite side through the roof to the cage, but the exo itself needs to let the shell OUT for replacement. Anyone think of a good way to do this? I was thinking I might be able to leave the back of the cage open, and slide the shell in from the back (pain in the ass, but possible, while keeping a tight cage?).

3. Should I just say **** the front end entirely, given the XJ's inner fender wells don't come out, and just tube in the whole front, sheet it over myself, and cut the firewall forward right out of the shell?

What say you oh fab gurus?

P.S. The BJ60 hybrid axles are almost exactly the same WMS as a 30/44, but with much larger offset. The runner frame I've got built now, has a 110" wheel base which is identical to my XJ. The only real concern would be that the wheel arches don't match up to engine placement, but it looks pretty close. I'd be tubbing the rear as far forward as I can without taking out the rear seat, and the front would be tight to the firewall. Should let me keep my 110" WB which has treated me very well.

just build a nice, well tied in and braced cage. i have never seen a unibody swapped onto a frame that didn't look like hacked together garbage.
Plenty of guys with heavier rigs, and hybrid cages do just fine.
Seen several flops and a few light rolls. If it's built fight all you should need after a light flop/roll is a header panel, maybe a fender, possible glass (?) and a fresh pair of underwear....
Why not just build an all out buggy that's still weather tight? Sounds easier to do then what you want to do. I can't see a body being "easy" to replace with all that work. Or, build a buggy chassis and cage, then take an xj body, hack the entire bottom out then slip it over the top kinda like an RC car I spose.
I like that idea....
Something like wide open designs new tj/yj chassis
Take this with a grain of salt but why not just buy a K5 Blazer(bob/dovetail it) or Land Cruiser and build from there(existing frame and plenty of room)? Sounds like you will need 1 ton axles to run 40s anyways. I thought FJ80 axles are considered the best?
In 1998 this would have been a discussion since folks thought paper thin mini truck frames were beef and unibody would fold if wheeled ...they also thought you needed a foot of space above the tire to flex.
I had wanted to do this years ago when I first got into XJs. My thoughts at that time were to build a cage for it and tie it into the sides and roof, cut the floor completely out of it and attach it to the frame. Then just run some sheet metal for a floor. Similar to what you would do making a buggy. You would basically just be putting a full XJ skin on it.
So your essentially building a 4 runner. Sounds like a huge PITA to simply have an XJ shell slapped on there for looks. As said before, a correctly built tube structure would negate any need for a frame.

Sounds like a huge project for what would essentially be a truggy. But again, to each their own.
So after pondering this for a while, I did end up building a runner truggy. Fully street legal, handles buggy trails pretty well. The benchmark around here is a trail called Fuct, which my v8 Xj managed, but definitely incurred some minor carnage and took a good 30 minutes to clear. The new Runner build did it in 10 minutes, and more than half that time was spent waiting in line.

So I keep coming back to what to do with the XJ though. It's killing my entire soul to have it sit on the lawn, I don't want to strip it because 90% of the work is really just unibody/armor/suspension that can't be removed and I don't wanna just scrap it, and no one around here is able to differentiate between a mild build lego XJ with a cheap lift kit and flares, against my V8 XJ, so I'd be hard pressed to get more than $4k for it (that's Canadian Pesos).

Now after my Runner build though, I've got a TON more skill and experience to come back to an XJ. I fired it up for the first time in 6 months. Runs like a top. Everything about the XJ just feels better. The runner is capable, but there's just no way to fit a bigger steering gear in it, and the toy boxes don't flow fast enough to power the ram the way I'd like. I also think I could build the XJ even lower than the Runner, while still getting more ground clearance.

So today I've been pondering just how much work it'd be to fab up another set of BJ60 axles (oh, these axles are the ****in' BOMB btw... I won't do tons on another light truck ever again), and stick'm under the XJ with some 40's, just to see how it feels. I'd pretty much just have to do some minor clearancing for the tires, weld on bracketry on the front axle for coils, arms, and track bar, fab up a tie rod with a GM 1 ton on the pitman side and toy 80 series on the axle end, and I think that's about it. Could be done in a day or two's work.

So going to bring home a dealer plate this week, take it to the scale, see if it's ACTUALLY the 5000lbs I measured last time. If it's under 4500, I may very well just throw the BJ60 axles under, cage it, and sell the runner.

FYI, regarding the bj60 axles. Seriously, guys. Look'm up and seriously consider them for a big XJ build. The engineering of the toy axles is just vastly superior to domestics. They're only marginally heavier than a 30/44, but stronger than a stock D60 when built properly. I dont' understand how so few guys have used them. Costs half what a domestic would cost to build, and you don't have to shorten them for an XJ.

Here's my runner from this weekend, vs my XJ on the same trail after the V8 swap.
(My runner is the bobbed/caged 2nd gen)

Anyhow, no hard and fast plan just yet. Just been eyeing up the 05 motor and 65e trans in the XJ and thinking about swapping it out for the runners 00 motor and 60e trans. The 05 motor is just so much snappier, and the 65e is 30% stronger. Then I fired up the XJ and fell in lust again and now just tossing ideas around. Helps for me to just write shit and ramble.