unibody strengtheners/use what when?

[Goatman]

What I've done (and it FEELS like it stiffened the body up) is:

rock rails, tied to the frame rail and pinch seam
RE drop brackets and braces; ties the LCA mount to the crossmember
HD front and rear bumpers, Mopar hitch in rear, both tied to "frame"
C-ROK plate at the steering box, and a MORE steering brace to the other side
RE HD trackbar/mount, with the optional brace to the other side

Not quite a cage, but it seems to be effective in combination...

Bill, I had all of that except the drop brackets and braces, and I did my own steering box frame plating (before C-Roks came out). Mine still cracked all to pieces. When I took off the rear bumper the rear cross member was cracked around nearly all of the bumper mounting holes.

Everything helps, and tying the control arm mounts to the rear spring hangers is a good thing to do. A couple of products do this, and there have been many good comments about T & J's stiffeners. Do what you can, but the only real way is a cage.

My experience is that nearly every time I stiffened up one part of the frame, something else cracked or broke off soon afterward. Here is an example of the most recent time. The bottom tube running to the end of the bumper was already there, but I added the upper tube and grill hoop, and the triangulated tube from the A pillar to the forward tube.

This broke on the very next trip, and you can see that the track bar bracket is thoroughly boxed, and the frame is boxed from the front crossmember to the motor mount.

By stiffening the whole front, which was the goal, now the frame around the track bar mount was left to flex on it's own, and it gave up the ghost to the 37's.

A new track bar mount brace is going on, the the steering box brace is going back on, now that the whole front is more rigid. I wasn't running either because I had previously ripped the track bar mount off while using a cross brace, and I ripped the steering box off (with the frame plated) while using a steering box brace. When the box ripped off it didn't hurt the frame, just broke two of the bolts and one of the bolt tabs on the box. That one really pissed me off, since it was a good Tommy Lee box less than a year old.

My point is to try and stiffen things up evenly, or the stress is just transfered to the weakest part. Not easy to do, but something to consider.

 

[MaXJohnson]

....unwad yer undies Max...

COMMANDO, baby:exclamati

 

[BrettM]

goatman,
hydro assist would take a LOT of stress off your steering box and trackbar mount I did mine for $110, and if I remember right, your box is already tapped for it....

 

[scorpion]

I was told sleeving the frame accomplished nothing really other than adding weight. I can understand plating the bottom so it doesn't get to bashed up on rocks but doing the whole outside isn't truly necessary. If you really want to strengthen the unibody then add a cage.

-Mike

I wouldn't say that sleeving the uni-body accomplishes nothing...

Back in the early 70's muscle cars came with a partial frame (the rest was a uni-body). My guess is that they did this to cut cost in building them but a nasty side effect was that they twisted up under the power of bigger motors. The gear heads eventually addressed this by cutting out by installing a sub-frame which wasn't much different than stiffeners. If you look around you'll see that man companies now sell sub-frame kits for them in the aftermarket.

XJ's obviously don't have the motor but with all of the flexing associated with driving them on and off road, the unibody also twists easily resulting in creaking and groaning. By adding some type of sub-frame you prevent the unibody from twisting as much and as a result, keep the twist in the suspension instead of the body.

Are they necessary? Depends...over time you can twist the unibody out of shape and your doors may not close well or at all. Installing stiffeners prior to this happening could prevent it down the road. When looking at the price that the vendors are selling them for, it's a rather inexpensive way to cure the problem before it exists.

Many of the aftermarket trends in cars have made their way to 4x4's over the years...

 

[Gojeep]

Just a thought here, trying to find an easy way to give more torsional stiffness. So you need more horizontal in the stiffener as well as the vertical. Adding cross members will help a lot here but was thinking along the lines of first angle or C section over the rail between the suspension mounts, but then adding plate to run from the bottom of that up to the back of the floor seam. You could then bolt to the seam in a similar way that many rock rails do with 1" box section and some full length flat on the other side? Just seems to me this would add a lot of strength to that seam where the floor and rocker panels meet which holds a lot of the strength in the body structure.

Any comments?

 

[Detour]

Sounds like scorpion has been down the same path as myself.
While totally different conditions, the results are the same.

Vertical stiffness is where its at, now if you can box a large floor pan area,
lets say out to your pinch lips, at the same time.....youre now accomplishing
something, leaving basically your tunnel area to flex, which is full of seams &
bends in your XJ, unlike your area from the the unibody.....out.

The one inch box tube is'nt a good suggestion.........take a 60" pcs of 1X1
tube or even the round tube others sell as a system.........stuff a few inches
of it under something that wont move...or in a secure vise. Push or pull on it,
if it flex'es......its going to flex on your rig. Take what we use 1.5" x 3" rect.
tube and try the same thing...........good luck. Horizontal stock can prevent
dent damage, but little or nothing more......try the same test.

Only thing I see left out here is that a number of companies such as Moroso
also offer total rear frame replacement rails, (Made from rect. box tube) for
uni-body street burners to handle the tork produced, they tie to the mid
section of the unibodies, so now you have a front clip and a rear clip of real
frame work....some are narrowed to accept larger rubber slinging tires........
...to make it complete, the bodies uni-body also also requires a sub frame or
stiffner......Two very different projects, but we both face the same end result.

 

[prerunnerXJ]

T&J performance makes some unibody stiffeners with built in sliders as an option

stage 1 kit:
http://tandjperformance.com/products-bpp-xj-chassiskit.htm

stage 2:
http://tandjperformance.com/products-bpp-xj-stage2chassiskit.htm

 

[gearwhine]

What are you trying to accomplish?

These frame sleeves will help protect the frame, but won't help too much as far as the frame flexing torsionally.

THANK YOU!

I tried to get my point across in a previous post a month or so ago, but don't think anyone even paid attention to what I said. No matter how much material you add to the frame rails, it's not going to do it's job to the fullest without cross supports....as you have already said.

I've plated my frame from the CA's to the leaf springs, but it is just to have solid mounting for brackets/cage/crossmembers/control arms etc.

_nicko_

 

[jxj]

I like the idea of Detours frame stiffeners/rock sliders. I wanted to know which transfer case skid will fit with the Detours setup? I like DPG/Rocklizard's transfercase skid but don't think it will fit. Any suggestions?

 

[floppy]

i searched and have a related question to this old thread...
my doors creak and sqeak on the simplest of trails, can I remedy this with a pair of C4x4 rock rails and a front tow hitch from jcwhitney?