bwfdrums

just get some frame stiffeners and call it a day.

BowtieGuy3

X2 on that...

Fen

The very fact you're the only person on the planet I've seen try to suggest the XJ is in any way "body on frame" tells me you aren't the most knowledgeable on this.

I'm not going to say all because I haven't seen everything, but the vast majority (and quite possibly all, especially 80's designed) monocoque vehicles use 2 box section rails running longitudinally close to the sides with lateral or cross braces where required. I'm really struggling to understand what can be vastly different on the XJ, especially as I haven't spotted it when I've been under mine.

Where I work is of no relevance. I've lost count of the number of times internet "experts" have pulled the "I do this for a living, what do you do" card when I have disagreed with them, You know who is usually (perhaps always) right? Clue: not the guy who does it for a living.

ulendo

clue - I dont particularly care what you think of me. nor do I care if you recite every piece of inflamatory BS you've heard on the internet. I've probably been wrenching on these rigs for longer than you've been around...cant be bothered to your bio either.

3rd party source - go look it up at your local technical college, or university engineering department, and/or have someone explain the techncial definitions of monocoque, body on frame, and unibody to you. body on frame, and unibody are not the same.

as for not feeding the trolls, and actually keeping on track, the location of the supports and bracing is what makes one structure stronger than another...thus why some aircraft can sustain significant damage and still fly, while others seem to just fall apart the first time a rivet fails. The XJ setup is similar in concept, and very, very solid, in 2, or 4 door form. Which is stronger isnt necessarily cut and dried either, as strength in one plane can & will effect rigidity in other axis. I dont have access to the OEM CAD plats, otherwise I could run a structural analysis on them on the work computer, and actually show the results.

Fen

My interest is in the info on here being factually correct. What I think of you is of no relevance, neither was it alluded to in my previous post, largely because I hadn't even considered it. I'm not trying to make it personal, I'm not trolling and I'm not, so far as I can tell, saying anything inflammatory beyond pointing out that you have made a statement that is incorrect.

Unibody is not the same as body on frame, I agree 100%, always have and didn't say any differently. What I did say is that while the whole world seems to agree that the XJ is unibody you are saying it is body on frame. It isn't, in the same way a football isn't a helicopter.

ulendo

so show me a parts diagram with the front and rear suspension support subframes...by definition, on unibodys, the subframes unbolt....

ulendo

on quick edit here - I just looked up a couple of things and found that the British VS American definitions are different... when I refer to Unibody, It would mean structures like the US Mustang 2, and GM bodies with removeable subframes, and the stressed structure a part of the sheetmetal. Body on frame to me would refer to a structure with welded or riveted in longitudinal members rather than a conventional ladder frame or chassis with soft mounted body for NVH control....

what are your definitions?

Fen

I wouldn't normally use the term unibody; I'd use monocoque, but my understanding is that they are one and the same. In many areas North American English has differences to British English and Kiwi English and Aussie English. If what you guys from the US mean by unibody is not the same as I mean by monocoque then I have misunderstood.

If my history isn't failing me the first monocoque car was the original Mini in the fifties. Minis use not one but 2 subframes (one each end). Most cars I have owned (I'm relatively new to 4wd) havehad a separate front crossmember which carries (typically) the motor mounts, front suspension (or perhaps just the bottom part of it with the McPherson strut tops in the body) and steering. The rear setup is frequently attached direct to the body though not in all cases.

I wouldn't consider the presence or lack of subframes or crossmembers to be the key being to monocoque (and hence unibody). The key in my eyes is that there is no stressed member between the front and rear ends of the vehicle apart from the body.

Basically I see there being two ways to construct a vehicle:

• Unbody/monocoque/unitary where the components are attached to the body and that body is stressed. Whether or not the components are grouped together into assemblies that are then mounted to the body or attached indivudually is secondary. Similarly the methid of constructing the stressed body is not a primary consideration.
• Body on frame where the components are attached to a frame or chassis and the body is bolted on top as an unstressed section.

So, are we trying to agree but being separated by our common language?

ulendo

probably.tyre vs tire is easy to work with. hood is not. hotchkiss drive...dont even go there.

I'm originally from the UK, live in Canada, and have to deal with american aftermarket companies providing kits for metric vehicles on a daily basis: definitions vary wildly.

OAS

O.K. , let's clear this up.

IF the Cherokee IS truley "body on frame", please post a link to a XJ body lift kit.


I know i know............

99XJDad

How about lets just call it a body over frame styled unibody and call it a day?

BowtieGuy3

From the Chrysler 1992 XJ/MJ/YJ Factory Service Manual:

Section 13-1
MJ/XJ Unibody Construction

"Jeep XJ vehicles (fig. 1) and the cab section of Jeep MJ vehicles (fig. 2) do not have a conventional frame. Both are constructed as a unitized body and frame (i.e., the body and the frame are constructed as a unit). The cargo box for the MJ vehicles (fig. 3) is attached to a semi-conventional frame that joins with the cab unibody.
Jeep XJ/MJ unibodies are constructed from special high-strength steel and coated metals. These special types of metals reduce weight and provide the necessary strength to withstand the forces applied against the structural members. The structural members collectively provide a unibody that has great structural strength"

ulendo

great..but you totally missed the issue. The US manuals/documentation use American english. The EU manuals have different classifications, and it sounds like auz/NZ may differ again. The manual for the Xj's built for the french marines, for example, refers to it as body on rail construction when specifying what damage leaves it still driveable, and what is structurally unsound.

the miscommunication arrived from the fact that the term 'body on frame' is also used in the US, but for an alternate setup. Seeing as neither myself, nor Fen are in the US, it was just a matter of clarifying local definitions. eg: my reference to the word 'hood' which means a convertible top in the UK, vs a bonnet, which is whats called a hood in the US.

Fen

Actually I'm a recently expat Brit as well, so I don't know what things are called in NZ for sure. For example I bought brake "rotors" yesterday, though I asked for "disks".