TJ vs LJ: a few thoughts

Vasq said:
How come no one ever bobs the LJ? I feel like I never see that done?
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People use to bob Scramblers but as Jeff (NashvilleTJ) said once you do it now requires a custom top. When I was looking at stretching my body I wasn't worried about a top since I was gunna run a half cab top. But like you know there are just some trails that aren't even stock LJ friendly.
 
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AndyG said:
@Wildman is another guy on here that has some experience and is totally unselfish....good dude.
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Thanks Andy,
I try to only stick my nose in on the ones where I have some knowledge or experiance. IMO this is what these forums are suppose to be about. Helping each other out and sharing knowledge.

Of course then there are those times it's fun to also be a smartass...

Keep us posted on that monster TJ you got.

Have fun with the better colored TJ too.
 
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Wildman said:
Thanks Andy,
I try to only stick my nose in on the ones where I have some knowledge or experiance. IMO this is what these forums are suppose to be about. Helping each other out and sharing knowledge.

Of course then there are those times it's fun to also be a smartass...

Keep us posted on that monster TJ you got.

Have fun with the better colored TJ too.
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Im on it....we are headed home from a jeep event in Townsend Tn, @Hog, @John Cooper, Nick, Ready Freddy and Carter Boo Boo and I had a blast.

Gorgeous weather...good times.
 
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mrblaine said:
The TJ frame is just slightly stiffer than well done pasta. If you set jack stands under each end of the frame and then unbolt the body mounts, the frame will droop in the middle more than you would expect.
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Somehow missed this thread and this came up when I looked up something else.

One question for you Blaine - what you describe above must atleast to some extent, be intentional from the designers, right? From what I have tried to understand, the body and the frame when bolted together in the right way unitize to make the combination good enough for most normal road/trail use. Is that understanding correct? Or would we have benefited better from a stiffer frame than what the factory gave us?
 
psrivats said:
Somehow missed this thread and this came up when I looked up something else.

One question for you Blaine - what you describe above must atleast to some extent, be intentional from the designers, right? From what I have tried to understand, the body and the frame when bolted together in the right way unitize to make the combination good enough for most normal road/trail use. Is that understanding correct? Or would we have benefited better from a stiffer frame than what the factory gave us?
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If you look at a standard TJ frame...it is pretty bereft of cross-members. There are really only three welded to the frame rails (front tube, rear bumper cross-member, and the rear shockmount. They bolted the transmission skid in as another crossmember. The way the torque boxes are designed on the tub makes me think that they did intend for the tub to help "unitize" the frame a bit.

I read a jalopnik article recently talking about the difference between a traditional body on frame pickup truck, like the Tacoma or Colorado (and the full-size versions) and a uni-body "truck" like the Honda Ridgeline. I think you'd enjoy it...

https://jalopnik.com/mid-size-trucks-dont-need-frames-1785674405
Anyway, in short, the design considerations of the ladder frame vs the unibody are interesting. The sail panels on the Avalanche (and first gen Ridgeline) are there to stiffen the body so frame twisting doesn't rip the body apart. If you think about a traditional Pick-up, the bed is seperate from the cab. That means the frame can twist and move a bit, and the two body sections are free to move independently of one another.

Bringing this back around to the TJ...without doorframes and no real B-pillar to speak of (and a folding A pillar), I'd bet the tub would tear itself apart in short order if you were to run without the roll bar bolted in (and the upper spreaders connected to the windshield). Everything is a system...designed to work together. Start changing it and you better be thinking about EVERYTHING that its connected to. Pretty interesting discussion to follow on the FB TJ-6 page when @mrblaine posted his question about extending the torque boxes for his TJ-6 project.
 
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Thanks, that Jalopnik link is interesting, reading it now.

Mike_H said:
Bringing this back around to the TJ...without doorframes and no real B-pillar to speak of (and a folding A pillar), I'd bet the tub would tear itself apart in short order if you were to run without the roll bar bolted in (and the upper spreaders connected to the windshield). Everything is a system...designed to work together. Start changing it and you better be thinking about EVERYTHING that its connected to. Pretty interesting discussion to follow on the FB TJ-6 page when @mrblaine posted his question about extending the torque boxes for his TJ-6 project.
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I am fascinated with how much intricacy and goodness is there in the factory TJ design. What you are above saying makes sense .. but it bring another question to my mind. Was this (ie tubs getting distorted) a problem on earlier jeeps with no rollbars? Or was the design sufficiently different (frame design/thickness and the way the body was mounted) and the usage much less harsh than what we put TJs through today that it did not matter that much?

I am a newish member on that TJ6 group and I will go look for that post/discussion you describe. Blaine also posted another question fairly recently reg. a 4th body mount and the some of the comments were seriously stupid.
 
psrivats said:
Thanks, that Jalopnik link is interesting, reading it now.



I am fascinated with how much intricacy and goodness is there in the factory TJ design. What you are above saying makes sense .. but it bring another question to my mind. Was this (ie tubs getting distorted) a problem on earlier jeeps with no rollbars? Or was the design sufficiently different (frame design/thickness and the way the body was mounted) and the usage much less harsh than what we put TJs through today that it did not matter that much?

I am a newish member on that TJ6 group and I will go look for that post/discussion you describe. Blaine also posted another question fairly recently reg. a 4th body mount and the some of the comments were seriously stupid.
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Same discussion. He had to extend the torque box to pick up the fourth body mount.
 
Mike_H said:
Same discussion. He had to extend the torque box to pick up the fourth body mount.
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Gotcha .. there is more to that torque box extension than meets the eye.

That jaloponik article was a good read. The comments section in that article has a good bit of discussion as well, going through that now. The points about the "sail panels" in the Avalanche/older Ridgeline was really interesting and educational. I have a few questions that I am going to mull over in my head, will hit you up on those later.

All this now makes me want to find articles as to what Ford did in the Maverick.
 
Mike_H said:
If you look at a standard TJ frame...it is pretty bereft of cross-members. There are really only three welded to the frame rails (front tube, rear bumper cross-member, and the rear shockmount. They bolted the transmission skid in as another crossmember. The way the torque boxes are designed on the tub makes me think that they did intend for the tub to help "unitize" the frame a bit.

I read a jalopnik article recently talking about the difference between a traditional body on frame pickup truck, like the Tacoma or Colorado (and the full-size versions) and a uni-body "truck" like the Honda Ridgeline. I think you'd enjoy it...

https://jalopnik.com/mid-size-trucks-dont-need-frames-1785674405
Anyway, in short, the design considerations of the ladder frame vs the unibody are interesting. The sail panels on the Avalanche (and first gen Ridgeline) are there to stiffen the body so frame twisting doesn't rip the body apart. If you think about a traditional Pick-up, the bed is seperate from the cab. That means the frame can twist and move a bit, and the two body sections are free to move independently of one another.

Bringing this back around to the TJ...without doorframes and no real B-pillar to speak of (and a folding A pillar), I'd bet the tub would tear itself apart in short order if you were to run without the roll bar bolted in (and the upper spreaders connected to the windshield). Everything is a system...designed to work together. Start changing it and you better be thinking about EVERYTHING that its connected to. Pretty interesting discussion to follow on the FB TJ-6 page when @mrblaine posted his question about extending the torque boxes for his TJ-6 project.
Click to expand...
If you want to see a TJ tear itself up in a certain area, run one without a tailgate. The taillight panels will separate from the torque box above the rear crossmember in short order. Oddly, there are only a few spot welds that tie the rear of the tub on either side of the tailgate to that torque box on each side. Even with the rear cage bolted down correctly, those spot welds will rip out of the sheet metal in a hurry.

Given what is involved in building a TJ-6, I was very surprised at the responses. I expected much better.
 
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mrblaine said:
If you want to see a TJ tear itself up in a certain area, run one without a tailgate. The taillight panels will separate from the torque box above the rear crossmember in short order. Oddly, there are only a few spot welds that tie the rear of the tub on either side of the tailgate to that torque box on each side. Even with the rear cage bolted down correctly, those spot welds will rip out of the sheet metal in a hurry.

Given what is involved in building a TJ-6, I was very surprised at the responses. I expected much better.
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I run without a tailgate, so I will be keeping eye on this area. I had a CJ7 for years that I beat on without a tailgate and no issues, I know comparing apples and oranges, but now I’m curious how the construction of that area differs. It’s been too long since I’ve had a CJ to compare.

On my TJ I do have a horizontal tube running between the 2 C pillars close to the plate, curious if that is enough to stiffen up the cage to help with the removal of the tailgate, or does that add more stress to that area. Thoughts?
 
Superjay5 said:
I run without a tailgate, so I will be keeping eye on this area. I had a CJ7 for years that I beat on without a tailgate and no issues, I know comparing apples and oranges, but now I’m curious how the construction of that area differs. It’s been too long since I’ve had a CJ to compare.

On my TJ I do have a horizontal tube running between the 2 C pillars close to the plate, curious if that is enough to stiffen up the cage to help with the removal of the tailgate, or does that add more stress to that area. Thoughts?
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Sometimes it just doesn't pay. I try, and I mean I really try to cover all the bases when I post something and in this case, it is abundantly clear that I failed to mention that running without a tailgate is not the same as running without a tailgate and doing something that ties the two sides back together like the tailgate does when it is closed and latched.
 
mrblaine said:
Sometimes it just doesn't pay. I try, and I mean I really try to cover all the bases when I post something and in this case, it is abundantly clear that I failed to mention that running without a tailgate is not the same as running without a tailgate and doing something that ties the two sides back together like the tailgate does when it is closed and latched.
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Thanks Blaine, I guess I was just curious if you thought tying the C pillars together was a good “fix” for removing the tailgate, or if it could stress that area out even more.
 
Superjay5 said:
Thanks Blaine, I guess I was just curious if you thought tying the C pillars together was a good “fix” for removing the tailgate, or if it could stress that area out even more.
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It is duplicating the function of a closed tailgate so you are not effectively running without a tailgate.
 
mrblaine said:
If you want to see a TJ tear itself up in a certain area, run one without a tailgate. The taillight panels will separate from the torque box above the rear crossmember in short order. Oddly, there are only a few spot welds that tie the rear of the tub on either side of the tailgate to that torque box on each side. Even with the rear cage bolted down correctly, those spot welds will rip out of the sheet metal in a hurry.

Given what is involved in building a TJ-6, I was very surprised at the responses. I expected much better.
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That really surprises me. I wouldn't think the latch mechanism has enough hold and location ability to make the tailgate structural. It makes total sense though... The tailgate prevents the two walls from falling into one another.
 
Mike_H said:
That really surprises me. I wouldn't think the latch mechanism has enough hold and location ability to make the tailgate structural. It makes total sense though... The tailgate prevents the two walls from falling into one another.
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Take a close look at the strike pin. There is a reason it has that big washer on the end of it which just sneaks by the side of the latch claws. Also why the strike mount on the tub is slightly angled, fairly robust and mounts to the strongest part of the inner fender. They designed it to close and lock the gate in with as little lateral movement as possible.
 
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Mike_H said:
That really surprises me. I wouldn't think the latch mechanism has enough hold and location ability to make the tailgate structural. It makes total sense though... The tailgate prevents the two walls from falling into one another.
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When I did have a CJ many moons ago, I remember one time I got stuck on a hill all twisted up, I had to open my tailgate to get some gear, was hard to get the tailgate to open. It was impossible to shut! The tailgate opening was being twisted in a way that the opening was to small to now close the tailgate. Wasn’t until I got to flatter ground that I could shut it. I know this was a CJ, but that was my first experience on how much the tub and that area could move… just an observation.
 
mrblaine said:
Take a close look at the strike pin. There is a reason it has that big washer on the end of it which just sneaks by the side of the latch claws. Also why the strike mount on the tub is slightly angled, fairly robust and mounts to the strongest part of the inner fender. They designed it to close and lock the gate in with as little lateral movement as possible.
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I did notice that when I replaced my tub, but didn't give it much thought. Thanks for that tidbit of information. Makes me want to figure out another solution for my spare tire now...its real hard to give the tailgate enough force to latch it fully without having the tire flex in and smash my hand. Pretty annoying.
 
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