what are the limits of the frame??

I live in Venezuela and many people prefer toyota because the cherokee doesn´t have shassis, and the frame is not strong, what are the limits of the frame?? what could someone do to fix this problem??

JulioCesar said:

I live in Venezuela and many people prefer toyota because the cherokee doesn´t have shassis, and the frame is not strong, what are the limits of the frame?? what could someone do to fix this problem??

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sleeve the frame rails

brandon
PS, do a search before ya post... many of these issues have been covered

I guess it depends on what you consider strong.

A unibody chassis is actually a lott stiffer and quite a bit lighter than any framed vehicle. The problem lies with longevity. Due the nature of the stiff unibody chassis any rusted area, crack from a collision, manufacturing defect etc becomes a very large stress concentration which can lead to cracking. Once the cracks have begun the stiffness of the unibody is lost quickly and since the material used for the unibody is quite thin repairing it can be difficult. This thin material also means rust can take it's toll much quicker when compared to a thick frame.

So, the "strength" of the vehicle depends a lot on it's age, it's prior use, rust etc.

Buy a Toyota?

You sure do ask some hokie questions.

shimmy said:

sleeve the frame rails

brandon
PS, do a search before ya post... many of these issues have been covered

Click to expand...

RedBluffBoy said:

Buy a Toyota?

You sure do ask some hokie questions.

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Damn, guys, give him a break. He's asking a very legitimate question. I hate the "do a search" reply. This isn't a bad topic to cover now and then. What, is there some rule that if something has been discussed a few times it has no right to be discussed again?


Like Bender said, a unibody is usually stiffer than a framed vehicle, especially the older C channel frames. The XJ does have a few weak points where cracking will occur over a good period of time of hard use. The first thing is to try and have a flexy suspension so most of the articulation is absorbed by the suspension rather than the frame. This includes control arms with flexible joints, like Johnny Joints or heim joints, and not poly bushings. It also helps to not wheel with the front sway bar hooked up, which transfers twisting force to the frame when it is hooked up.

It seems that stiffening between the front and rear suspension points is a good thing. You can sleeve the frame rails, or box in next to the frame rails running from the leaf spring hanger to the lower control arm mount. You can also get the frame stiffeners from T&J Performance. The ultimate way to stiffen the body is by installing a cage, but not everyone has the capability to do that. There are more pre-fab cages on the market now, including a nice one from T&J.

It's best to add some stiffeners to the rig right away if you're doing a build up. I ran mine without any stiffeners for about six years of very hard use with no signs of cracking. But, when the cracks did start to happen I got all kinds of them. It's much easier to do some reinforcing up front than it is to weld up cracks, repaint, and then also add reinforcement.

If you're curious, here's a list of all the places I've had cracks. At the top of the front crossmember on both sides where it attaches to the top of the frame. Around the steering box, outside, top, and bottom of the frame. About 4" back on the frame from the track bar mount, where the frame begins to flare wider....V shaped crack from the bottom up both inside and outside. At the top of the front frame section where it meets the firewall. On the A pillar just above the upper door hinge...both sides. On the A pillar about 4" up from the bottom of the windshield. At the top of the A pillar, almost all the way around from the drip rail to the inside lip.....both sides, multiple times. On the floor under the back seat in multiple places. Between the mounting holes for the rear bumper on the rear crossmember. I've also seen the latch plate on the bottom of the rear hatch rip out of a couple of rigs. I cut out some simple strips of sheetmetal, bent it to form next to the plate, and riveted them in on both sides, and never had a problem.

Frame cracking, and ripping steering boxes off the frame, occures in nearly all framed vehicles as well. Hard use causes metal fatigue no matter what you're driving.

Goatman said:

It's best to add some stiffeners to the rig right away if you're doing a build up. I ran mine without any stiffeners for about six years of very hard use with no signs of cracking. But, when the cracks did start to happen I got all kinds of them. It's much easier to do some reinforcing up front than it is to weld up cracks, repaint, and then also add reinforcement.

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Does a good set of rock rails help with frame rigidness, or are they just for protection? The ones I have attach to the pinch seam and the frame rail, so it seems it would add SOME stiffness.

BillR said:

Does a good set of rock rails help with frame rigidness, or are they just for protection? The ones I have attach to the pinch seam and the frame rail, so it seems it would add SOME stiffness.

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Well the stiffen up each side, but whatever flex/twist you had between the sides, for the most part is still there. To stiffen up the sides against each otehr you'd want to put crossmemembers between the frame rails, or if you sleeved the whole frame you can stiffen up using the front and rear bumpers and with a single crossmember in the middle. Cage also helps with the rigidness.

Goatman said:

Damn, guys, give him a break. He's asking a very legitimate question. I hate the "do a search" reply. This isn't a bad topic to cover now and then. What, is there some rule that if something has been discussed a few times it has no right to be discussed again?

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Your right, my apologies to you JulioCesar.
Like Mama says if you can't say nothing good don't say nothing at all.

Goatman said:

Damn, guys, give him a break. He's asking a very legitimate question. I hate the "do a search" reply. This isn't a bad topic to cover now and then. What, is there some rule that if something has been discussed a few times it has no right to be discussed again?


Like Bender said, a unibody is usually stiffer than a framed vehicle, especially the older C channel frames. The XJ does have a few weak points where cracking will occur over a good period of time of hard use. The first thing is to try and have a flexy suspension so most of the articulation is absorbed by the suspension rather than the frame. This includes control arms with flexible joints, like Johnny Joints or heim joints, and not poly bushings. It also helps to not wheel with the front sway bar hooked up, which transfers twisting force to the frame when it is hooked up.

It seems that stiffening between the front and rear suspension points is a good thing. You can sleeve the frame rails, or box in next to the frame rails running from the leaf spring hanger to the lower control arm mount. You can also get the frame stiffeners from T&J Performance. The ultimate way to stiffen the body is by installing a cage, but not everyone has the capability to do that. There are more pre-fab cages on the market now, including a nice one from T&J.

It's best to add some stiffeners to the rig right away if you're doing a build up. I ran mine without any stiffeners for about six years of very hard use with no signs of cracking. But, when the cracks did start to happen I got all kinds of them. It's much easier to do some reinforcing up front than it is to weld up cracks, repaint, and then also add reinforcement.

If you're curious, here's a list of all the places I've had cracks. At the top of the front crossmember on both sides where it attaches to the top of the frame. Around the steering box, outside, top, and bottom of the frame. About 4" back on the frame from the track bar mount, where the frame begins to flare wider....V shaped crack from the bottom up both inside and outside. At the top of the front frame section where it meets the firewall. On the A pillar just above the upper door hinge...both sides. On the A pillar about 4" up from the bottom of the windshield. At the top of the A pillar, almost all the way around from the drip rail to the inside lip.....both sides, multiple times. On the floor under the back seat in multiple places. Between the mounting holes for the rear bumper on the rear crossmember. I've also seen the latch plate on the bottom of the rear hatch rip out of a couple of rigs. I cut out some simple strips of sheetmetal, bent it to form next to the plate, and riveted them in on both sides, and never had a problem.

Frame cracking, and ripping steering boxes off the frame, occures in nearly all framed vehicles as well. Hard use causes metal fatigue no matter what you're driving.

Click to expand...

Thanks a lot for your help my friend you are a good member of this site not like others

Bender said:

A unibody chassis is actually a lott stiffer and quite a bit lighter than any framed vehicle.

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sorry it just bugs me when people use this example.
a complete unibody is a lot stronger when it comes to twisting than any old style channel frame.
but, are you trying to tell me that the same channel frame is weaker when you bolt the body to it? lets just use an old chebby truck as an example, back when the sheetmetal was thick. an old beefy truck like that is like a unibody with a frame bolted to it imo.
basically what i am trying to say is that the xj unibody is stronger than some frames, but not complete body+frames.

p.s. how can there be limits for something that doesn't exist?????? :laugh3:

I wasn't referring to overall strength but rather stiffness. Generally a body on frame vehicle has bushings between the body and frame. These bushings deflect taking away from the vehicles stiffness. Also the bed is generally seperate from the cab on pickups which takes away from its overall stiffness a great deal.

Would the XJ unibody be stronger?? no. But I'd say it would be stiffer.

xj_punk said:

sorry it just bugs me when people use this example.
a complete unibody is a lot stronger when it comes to twisting than any old style channel frame.
but, are you trying to tell me that the same channel frame is weaker when you bolt the body to it? lets just use an old chebby truck as an example, back when the sheetmetal was thick. an old beefy truck like that is like a unibody with a frame bolted to it imo.
basically what i am trying to say is that the xj unibody is stronger than some frames, but not complete body+frames.

p.s. how can there be limits for something that doesn't exist?????? :laugh3:

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Is a little educating due here?

The body on a full frame vehicle doesn't add rigidity because it's mounted with rubber body mounts. IF the body did add stiffness (which it doesn't) a pick up body wouldn't because it breaks between the cab and the bed........

Sorry it bugs you........now maybe it won't.

The body does add stiffness, actually, quite a bit. A suburban is much more rigid and less wiggly than a 1500 pickup, and they ride on the exact same frame. The suburban body is fully joined, while a pickup is not.

xj_punk said:

sorry it just bugs me when people use this example.
a complete unibody is a lot stronger when it comes to twisting than any old style channel frame.
but, are you trying to tell me that the same channel frame is weaker when you bolt the body to it?

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That's what I would tell you.

I'm on a lot of construction sites, and most contractors (and their employees) around here seem to favor full-size Ford and Chevy pickups. Look at just about any of their trucks more than a year or two old from the rear, and you'll see that the top of the tailgate isn't even close to parallel to the bottom of the rear window.

Which means the frame got tweaked.

i might get harassed here, but I would get a Toyota in your situation. Toyotas use a fully boxed frame here, it's very strong. However that's not my main reason, Toyotas for overseas markets (Hilux and multiple LCs) are way better than they are in the US. Diesel engines, solid axles, etc. I would also assume that the parts resources and aftermarket are way more oriented towards Toyota down there.

if you want to get an XJ, GREAT, we'll help you with it, but I would way rather have one of these:

or one of these: