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Old 04-09-2007, 03:35 PM   #1 (permalink)
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XJ Unibody reinforcement

I've been looking into reinforcing the Unibody structure of my XJ before I add a lift to it... I've found a few different options...


For the front example
http://www.temper-mentalracing.net/services.htm

For the middle example
http://www.tntcustoms.com/webv5/xjstiffeners.asp



But asking the local shops about weld on instalation, no one will touch it, saying the factory metal will weaken by welding that much to it, claiming it's a hardened steel (it made me wonder why they would be willing to weld on the suspension links)

so I got to thinking about essentialy welding these 2 peices together, then bolting it all on to the unibody using through bolt spacers, and connecting the suspension and cross members to it as though it was a subframe

Am I crazy?

are these shops being dumb?
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Old 04-09-2007, 04:12 PM   #2 (permalink)
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the shops are being safe, b/c if not done absolutely correct the unibody welds will crack and brend or break the unibody. Plus I dont know where u live but in some states its illegal to weld to the unibody anyway.
My opinion is start off with just the tnt kit and weld it on than drive it for awhile and see how the flex is affected and keep an eye on the welds for stress cracking, than play with the idea of the temper-mental kit.
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Old 04-09-2007, 04:29 PM   #3 (permalink)
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I wouldn't be too worried about it really, there are plenty of guys out there running those parts without problems. I've welded quite a bit to my frame without issues as well.
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Old 04-09-2007, 04:36 PM   #4 (permalink)
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Lots of stuff arround regarding XJ frame stiffening. Here's one I think is good: http://www.pirate4x4.com/forum/showt...highlight=TOTW
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Old 04-09-2007, 04:55 PM   #5 (permalink)
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I plated my "Frame" Uni body and have had no troubles. My doors still open...I also have a full cage which helps
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Old 04-09-2007, 05:15 PM   #6 (permalink)
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I used 3x3 angle iron and it's been perfect. I stitch welded the top 2" every 4" or so, then I rosette welded 10 spots per side then I added 4 - 3/4" bolts through the unibody per side also. I don't think its going anywhere.
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Old 04-09-2007, 08:25 PM   #7 (permalink)
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I am very n00b-ish when it comes to the unibody on our XJs, but could this work? Could you cut the bottom of the unibody rail off, and slide some box steel into the slot and bolt it to the unibody through the sides and the top? As long as the box steel was strong enough, you could tighten the bolts pretty tight without needing spacers to keep from caving the rails in.
(see cheezy picture)



I don't know how wide the rails are internally, so this may be mute. in theory, you could make a whole frame from the firewall back relatively "easy" that had stronger plate steel mounts for the suspension points and such. And if the rig was wrecked body wise later on, the "frame" could be unbolted and transfered to a new donor XJ. If you really knew what you were doing, you could possibly build the frame all the way to the front to hold the motor and all. Then, you would take an XJ, cut the framerails from the firewall forward off, cut the bottom of the rest of the rails out, slip the body onto your box frame, and bolt the fenders and front on. As long as the box steel frame was strong enough, cutting the bottom of the unibody rail shouldn't weaken anything, "in theory". Regular frame cars just bolt to a box frame in 4-10 places and hold fine. Once again, it may not be feasible for the time and effort involved as well as other unthought of things I don't know about, since I am relatively new to toying with XJs.



I just like to let the creative juices flow every now and then.

Last edited by BB1980; 04-09-2007 at 08:26 PM.
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Old 04-09-2007, 08:47 PM   #8 (permalink)
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Quote:
Originally Posted by Maytag View Post
I've been looking into reinforcing the Unibody structure of my XJ before I add a lift to it... I've found a few different options...


For the front example
http://www.temper-mentalracing.net/services.htm

For the middle example
http://www.tntcustoms.com/webv5/xjstiffeners.asp



But asking the local shops about weld on instalation, no one will touch it, saying the factory metal will weaken by welding that much to it, claiming it's a hardened steel (it made me wonder why they would be willing to weld on the suspension links)

so I got to thinking about essentialy welding these 2 peices together, then bolting it all on to the unibody using through bolt spacers, and connecting the suspension and cross members to it as though it was a subframe

Am I crazy?

are these shops being dumb?
not trying to promote any websites just trying to give some helpful info.
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http://board.marlincrawler.com/index....msg364044#new
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Old 04-09-2007, 10:59 PM   #9 (permalink)
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Quote:
Originally Posted by Maytag View Post
I've been looking into reinforcing the Unibody structure of my XJ before I add a lift to it... I've found a few different options...


For the front example
http://www.temper-mentalracing.net/services.htm

For the middle example
http://www.tntcustoms.com/webv5/xjstiffeners.asp



But asking the local shops about weld on instalation, no one will touch it, saying the factory metal will weaken by welding that much to it, claiming it's a hardened steel (it made me wonder why they would be willing to weld on the suspension links)

so I got to thinking about essentialy welding these 2 peices together, then bolting it all on to the unibody using through bolt spacers, and connecting the suspension and cross members to it as though it was a subframe

Am I crazy?

are these shops being dumb?
The particular shops you're talking to are being very conservative. I really don't think the extra heavy sheetmetal of our frames is "hardened steel". There have been so many of us that have successfully welded reinforcements to our frames that I would just do it and not worry about it. The companies that produce those parts that are meant to be welded on have more liability than a local shop that would do the welding. If you don't do the frame reinforcing, and you wheel hard or for a long time, you will eventually get stress cracks. Some of us have gone for a long time without cracks, but when they started showing up there were many of them. Experience shows that the best course of action is to add good extra bracing right up front to strengthen things up and avoid the cracks later on.

For those who might think this is unique to a unibody constuction, it happens to full frame rigs as well. I've done trail repairs on frames on CJ's and Toyota's as well as XJ's, and companies make frame strengthening plates for a wide variety of 4x4 rigs.
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Old 04-14-2007, 07:48 AM   #10 (permalink)
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Bump. Anyone on my idea?
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Old 04-14-2007, 08:24 AM   #11 (permalink)
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I read somewhere the XJ frame is made from high tensile steel, as apposed to mild steel.
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Old 04-14-2007, 10:23 AM   #12 (permalink)
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The steel strength varies section to section, as they felt it was needed.

I think the FSM explains what type of steel was used where.
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Old 04-14-2007, 11:17 PM   #13 (permalink)
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A bunch of angle welded to the rails is not very hardcore or advanced.

It's really just that much more booty fab.

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Old 04-14-2007, 11:43 PM   #14 (permalink)
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A bunch of angle welded to the rails is not very hardcore or advanced.

It's really just that much more booty fab.

--ron

OK mister super duper sheetmetal fab guy, show us how you did it.

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Old 04-15-2007, 10:34 AM   #15 (permalink)
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Bump. Anyone on my idea?
Yeah- sounds like way too much work. And if you want a scare sometime, put a basic c-clamp like you'd use for a brake job on the sides of your 'frame' rails and give it a little twist. This is why I think the reinforcements would need welding.
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Old 04-15-2007, 11:14 AM   #16 (permalink)
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Bump. Anyone on my idea?


Yeah, I agree that it's too much work. Plus, I wouldn't want to cut that much of the frame out in case the whole thing moved around while you're working on it.

A couple of things on stiffening the frame. It seems that people have good results strengthening between the front control arm mounts and the front leaf spring hangers. Adding structure is more important than just adding thick steel. Don't make the mistake of just adding a cage and or frame reinforcement just to the A pillars, there is a lot of flex from the A pillars forward. There is tremendous movement/twisting of the frame around the track bar mount, as well as the steering box. It seems to be a mistake to just stiffen certain parts of the chassis, since then flex becomes centered in the smaller sections that are un-reinforced resulting in cracks.

I think those front reinforcements from Temper-Mental look real good, as do the TnT frame stiffeners. The SBS reinforcment system from JKS is very good, easily the best available for the steering box, and they come for both sides.

One thing that's nice is that those who are building XJ/MJ's now can use this info and reinforce everything right from the start. Us old timers learned the hard way and have done it an element at a time, repairing stress cracks as we went.
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Old 04-15-2007, 11:36 AM   #17 (permalink)
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A bunch of angle welded to the rails is not very hardcore or advanced.

It's really just that much more booty fab.

--ron
I agree it's not Hardcore...

But it makes for a good spot to tie in a cage or sliders!
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Old 04-16-2007, 03:20 AM   #18 (permalink)
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OK mister super duper sheetmetal fab guy, show us how you did it.



For now, I found something to tease you with.



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Old 04-16-2007, 05:00 AM   #19 (permalink)
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For now, I found something to tease you with.



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Old 04-16-2007, 05:39 AM   #20 (permalink)
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I see the pic, and I have seen Captian Ron's sheet metal reinforcement elsewhere, and it's probably the best looking job ive seen. Not to say its the strongest or most hardcore, but it is def the most asthetically pleasing setup.
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Old 04-16-2007, 07:40 AM   #21 (permalink)
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For now, I found something to tease you with.



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The only thing you can tease me with is a working CNC machine.....

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Old 04-16-2007, 07:56 PM   #22 (permalink)
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Yep I see them now...file server must have been down?....

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Old 04-18-2007, 09:57 AM   #23 (permalink)
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If you know how to weld there shouldnt be a problem! Now if you dont know how to weld then dont weld to your UNIBODY!!!!!
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Old 04-18-2007, 10:39 AM   #24 (permalink)
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Quote:
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For now, I found something to tease you with.



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is that piece even on the MJ anymore?
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Old 04-19-2007, 01:09 AM   #25 (permalink)
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I have had no cracks on mine in the center section and it was welded years ago. I think I found a crack near where my front coil over hoops mount, thats pretty new to my rig. I might have to add more tubing, as it evolves you look for stress points and add material where needed.
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