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DrThunder

frame stiffeners

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Anyone run them? I know a lot of xj guys run them because of the full unibody. Does a comanche's unibody/frame flex enough to benefit from frame stiffeners?

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Not really. XJs need them because their uni-frame is pretty wussy and the flexing can cause cracks to appear in the body. MJs have a much beefier uni-frame up front, a fully boxed frame out back, and the rear wall of the cab acts like a diagonal brace. Bottom line, our trucks really don't have much need for them unless you're looking to pull some major air time. :D

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While I completely agree with Pete. As it pertains to a vehicle with stock suspension.

 

Yours is not a stock suspension.

 

The addition of your long arms does in fact move the forces of the suspension to areas not originally intended to take them. I do not meant to suggest there is or even could be a problem. Just since you brought it up, maybe a good look with an eye towards articulation/ stress forces may reveal and need for some additional bracing to re-enforce your particular setup.

 

CW

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I put them on mine. I haven't finished building it yet to see if there is a difference. I used 3x3x.25 angle and went from the firewall to just passed the rear of the cab. I cut out all the stock weld nuts in the frame and welded 1/2" nuts to the top side of the plates and then welded the plates on. I integrated the long arm mounts into them kinda too, made them bolt on and weld on, should help a lot. There are now nuts for the crossmember, skid plate, traction bar mount and front control arm mounts.

 

 

I bought the steel to do it to the XJ, but decided to build an MJ instead, so I had to use the metal for something.

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I will be plating my frame on my MJ. It's not that much stronger then a XJ. I just cut the front frame off of the cab on my MJ parts cab and was not impressed...

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when i chopped up the '86 i cut the cab from the "frame" then cut the front section of "frame" from the shocks forward *plenty of beef there* then cut from the foot forward *this is the smallest part of the "frame" and seems to be supported well by the cab* i then cut wedges from the inside of the "frame rails" just in front of the bed *as a whole this spot seemed very sturdy but when cut was pretty flimsey*

 

this truck was also in an accident t-boned a honda at 50mph and i was very close to just fixing the minimal front end damage.

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I have a tendency to get a little crazy at times. This means the frame will be plated. It will be much stronger and will be up to the task. I'm also hanging heaver axles and they will be trussed to be good to go, I just don't want to tweak the frame if I get some air or hit some rough sections of trail at speed. I might 4 link the rear next winter for about 20" of travel.

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I've been wondering if stiffeners would be a worthwhile investment... guess it really depends on what you plan on doing with it.

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I've been wondering if stiffeners would be a worthwhile investment... guess it really depends on what you plan on doing with it.

 

IMO If you run 33" tires or more and wheel moderately hard they are a good investment. Unless you don't plan on keeping your MJ for a year or two.

 

The front frame is the weakest area. The steering box area should be braced on both sides with 3/16" steel. I would plate the other frame rail across from the box the same way. A beefy bumper or front crossmember should tie the two sides together. Next would be a brace from the passenger frame rail to the trackbar mount. After that plating the outside of the frame from the steering box braces to the LCA mounts or to the back of the cab with 1/8" steel plate. Then plate the under side of the frame back to the LCA mounts or to the rear spring mounts, 1/8" to 3/16" will work. Doing the inside of the frame in the engine compartment with 12 gauge steel would be next. Weld in rocker replacements that tie onto the frame will tighten it up and save the body. A real crossmember and a belly skid will finish it up for the most part.

 

I plan on going nuts plating my MJ's frame and will be tieing it all together with a full roll cage from the front bumper to the rear bumper. I will also be tieing into the suspension mounts and rear shocks. It will make a great base for my front mid-arm 3 link.

 

You may think I'm crazy for doing all this but I will be confident it wil last and be ready for any other mods I add later.

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I've been wondering if stiffeners would be a worthwhile investment... guess it really depends on what you plan on doing with it.

 

IMO If you run 33" tires or more and wheel moderately hard they are a good investment. Unless you don't plan on keeping your MJ for a year or two.

 

The front frame is the weakest area. The steering box area should be braced on both sides with 3/16" steel. I would plate the other frame rail across from the box the same way. A beefy bumper or front crossmember should tie the two sides together. Next would be a brace from the passenger frame rail to the trackbar mount. After that plating the outside of the frame from the steering box braces to the LCA mounts or to the back of the cab with 1/8" steel plate. Then plate the under side of the frame back to the LCA mounts or to the rear spring mounts, 1/8" to 3/16" will work. Doing the inside of the frame in the engine compartment with 12 gauge steel would be next. Weld in rocker replacements that tie onto the frame will tighten it up and save the body. A real crossmember and a belly skid will finish it up for the most part.

 

I plan on going nuts plating my MJ's frame and will be tieing it all together with a full roll cage from the front bumper to the rear bumper. I will also be tieing into the suspension mounts and rear shocks. It will make a great base for my front mid-arm 3 link.

 

You may think I'm crazy for doing all this but I will be confident it wil last and be ready for any other mods I add later.

 

i disagree.

 

ive never heard of anybody having troubles with the frames while running 33s. i never ONCE considered it. even if you don't, i think your truck will last longer than a year or 2

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I've been wondering if stiffeners would be a worthwhile investment... guess it really depends on what you plan on doing with it.

 

IMO If you run 33" tires or more and wheel moderately hard they are a good investment. Unless you don't plan on keeping your MJ for a year or two.

 

The front frame is the weakest area. The steering box area should be braced on both sides with 3/16" steel. I would plate the other frame rail across from the box the same way. A beefy bumper or front crossmember should tie the two sides together. Next would be a brace from the passenger frame rail to the trackbar mount. After that plating the outside of the frame from the steering box braces to the LCA mounts or to the back of the cab with 1/8" steel plate. Then plate the under side of the frame back to the LCA mounts or to the rear spring mounts, 1/8" to 3/16" will work. Doing the inside of the frame in the engine compartment with 12 gauge steel would be next. Weld in rocker replacements that tie onto the frame will tighten it up and save the body. A real crossmember and a belly skid will finish it up for the most part.

 

I plan on going nuts plating my MJ's frame and will be tieing it all together with a full roll cage from the front bumper to the rear bumper. I will also be tieing into the suspension mounts and rear shocks. It will make a great base for my front mid-arm 3 link.

 

You may think I'm crazy for doing all this but I will be confident it wil last and be ready for any other mods I add later.

90% of which can be done with bolt-on things.

 

C-Rok & TNT Customs makes a nice steering support brace for the frame rail. RE makes a tracbar brace that attaches to their HD tracbar/mount. Many vendors make a nice steering box brace.

 

I can't say I've EVER seen or heard of someone ripping off a LCA mount; especially on the MJ since they are beefier than the XJ.

 

Only issue I see is with the LCA mounts on the axle itself but we're not talking about axle's here; were talking about the body.

 

Don't get me wrong I'm sure running "frame" stiffners is beneficial, but stating that your rig with 33's won't last more than 2 years is crazy talk. Heck I have 35's on my XJ and have wheeled the pi$$ out of it with no ill effects yet and do not have the stiffners (however have everything above that I stated). Yeah I'll probally run them sometime but thats on an XJ, not a MJ....

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I've been wondering if stiffeners would be a worthwhile investment... guess it really depends on what you plan on doing with it.

 

IMO If you run 33" tires or more and wheel moderately hard they are a good investment. Unless you don't plan on keeping your MJ for a year or two.

 

The front frame is the weakest area. The steering box area should be braced on both sides with 3/16" steel. I would plate the other frame rail across from the box the same way. A beefy bumper or front crossmember should tie the two sides together. Next would be a brace from the passenger frame rail to the trackbar mount. After that plating the outside of the frame from the steering box braces to the LCA mounts or to the back of the cab with 1/8" steel plate. Then plate the under side of the frame back to the LCA mounts or to the rear spring mounts, 1/8" to 3/16" will work. Doing the inside of the frame in the engine compartment with 12 gauge steel would be next. Weld in rocker replacements that tie onto the frame will tighten it up and save the body. A real crossmember and a belly skid will finish it up for the most part.

 

I plan on going nuts plating my MJ's frame and will be tieing it all together with a full roll cage from the front bumper to the rear bumper. I will also be tieing into the suspension mounts and rear shocks. It will make a great base for my front mid-arm 3 link.

 

You may think I'm crazy for doing all this but I will be confident it wil last and be ready for any other mods I add later.

 

i disagree.

 

ive never heard of anybody having troubles with the frames while running 33s. i never ONCE considered it. even if you don't, i think your truck will last longer than a year or 2

 

You must not have a good memory then because you know Pat. He just fixed some cracks in his frame and doesn't wheel much at all and has smaller tires then 33" ones...

 

Cracks are common around the steering box, the track bar mount and other high stress area's.

 

All of the above work isn't needed but some is. The main areas that need to be addressed is the steering box, front bumper anf track bar brace.

 

I'm not saying it will self distruct but it will develop stress zones that will crack. BTW if you ever plan on getting some air or hammering hard at speed it is needed. If you don't believe me check into JeepSpeed.

 

 

BTW, my MJ will be around for many years. The 4.0 HO engine it will get has 3032 miles on it. The AW-4 has 90k on it and has been well serviced/resealed. The NP242 is getting rebuilt, will have a wide chain,a stronger planetary gear set, the HD differential the 32 spline output shaft and a 241 SYE. The axles will be replaced with stronger ones that will be rebuilt,regeared, have alloy shafts and be trussed.

 

I will be looking for a daily driver this summer so my MJ will mainly be a toy. I plan on keeping it for at least 10 years, but most likely untill I die...

 

My '94 XJ I bought in early 1998 and my '95 was bought in mid 1999.

 

I don't sell my rides very often... But you don't know me well enough to know that either...

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...my frame break was probably partially my fault but we have no way of knowing at this point if I missed a small part of where I cut or not.

 

either way, frame breaks are quite common from what I've seen, and I've seen a few xj's with torn-off LCA mounts on the body-side

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90% of which can be done with bolt-on things.

 

C-Rok & TNT Customs makes a nice steering support brace for the frame rail. RE makes a tracbar brace that attaches to their HD tracbar/mount. Many vendors make a nice steering box brace.

 

I can't say I've EVER seen or heard of someone ripping off a LCA mount; especially on the MJ since they are beefier than the XJ.

 

Only issue I see is with the LCA mounts on the axle itself but we're not talking about axle's here; were talking about the body.

 

Don't get me wrong I'm sure running "frame" stiffners is beneficial, but stating that your rig with 33's won't last more than 2 years is crazy talk. Heck I have 35's on my XJ and have wheeled the pi$$ out of it with no ill effects yet and do not have the stiffners (however have everything above that I stated). Yeah I'll probally run them sometime but thats on an XJ, not a MJ....

 

I never said to beef the LCA mounts, just that the stiffiners would run to them or the back of the cab.

 

You have addressed the main areas where cracks happen thou...

 

If wheeled regularly for 2 years without any reinforcements cracks in the steering box area can happen, so can cracks by the track bar.

 

The stiffers help keep the body straight and help eliminate the cracks that can happen by the pillars on mainly on XJ's but have happened on MJ's also and in stop cracks in quite a few more areas on a XJ.

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I'm not the only one who feels this way...

 

Here is Jeff frame work so far. It will be back halfed with a 1/4 elliptic leaf spring 4-link suspension.

 

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I'm not the only one who feels this way...

 

Here is Jeff frame work so far. It will be back halfed with a 1/4 elliptic leaf spring 4-link suspension.

 

Well he's cutting the back half off, what do you expect?

 

I don't think the OP ever said they were doing the same..... ;)

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A word of caution. Don't let any moisture, especially, salty moisture get in there between the old frame and the plate. It will rust very fast. Double metal reinforcements are always the areas that rust out first. Over the years I've seen many 'patched' areas rust right out again because the old metal was not removed behind the patch. I remember that there are some 'weldable' precoat material to protect the steel. It will act like an insulator for the galvanic cell between the two layers of steel

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A word of caution. Don't let any moisture, especially, salty moisture get in there between the old frame and the plate. It will rust very fast. Double metal reinforcements are always the areas that rust out first. Over the years I've seen many 'patched' areas rust right out again because the old metal was not removed behind the patch. I remember that there are some 'weldable' precoat material to protect the steel. It will act like an insulator for the galvanic cell between the two layers of steel

 

If there are any areas moisture can get behind the the plates some 3M seam sealer and the proper finish being applied will stop this problem.

 

The weldable precoat is ok but sealing it properly is the cure.

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Well he's cutting the back half off, what do you expect?

 

I don't think the OP ever said they were doing the same..... ;)

 

He is plating the rear of the frame for the backhalf he is doing. The front of the frame is being done because of the flex it has just like XJ's do....

 

Anyone run them? I know a lot of xj guys run them because of the full unibody. Does a comanche's unibody/frame flex enough to benefit from frame stiffeners?

 

As you can read he asked about frame stiffeners and if the MJ unibody frame flexes enough to benefit from them. He also asked if anybody runs them and I was showing what other people are doing to stiffen the frame. I also replied with my plans I have for my frame.

 

You stated

90% of which can be done with bolt-on things.

 

C-Rok & TNT Customs makes a nice steering support brace for the frame rail. RE makes a tracbar brace that attaches to their HD tracbar/mount. Many vendors make a nice steering box brace.

 

Don't get me wrong I'm sure running "frame" stiffeners is beneficial, but stating that your rig with 33's won't last more than 2 years is crazy talk. Heck I have 35's on my XJ and have wheeled the pi$$ out of it with no ill effects yet and do not have the stiffners (however have everything above that I stated). Yeah I'll probally run them sometime but thats on an XJ, not a MJ....

 

The frame has issues with cracking and flexing which you admited is a problem. You use C-roks frame reinforcements and a RE brace to help solve the flexing and cracking problems.

 

Sheet metal can only be flexed so much, the more it flexes the weaker it gets and cracks are the result of the flexing.

 

If you were just back halfing a MJ the following pictures show about all the frame would be needed if the unibody flex wasn't an issue.

 

Btw, he also plans on reinforcing from the front of the frame to the end of the cab because of the lack of chassis stiffness the stock frame has.

 

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gonna bump this back up to the top. Those of you who have plated frames, has it worked? what would you have done differently?

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A friend of mine reinforced the frame on his Cherokee front to back. Don't know if it is because of this and forces being transmitted through the body, but when he set a frame rail down on a rock pretty hard it caused the windshield to crack. Thinking the original unibody (without 1/4" thick plating) might have dented enough to absorb some of the impact and prevent this.

 

I know I have a good number of dents in the "frame rails" and never cracked a window yet unless from contact with a tree or a rock.

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shouldn't xj stiffeners work on a mj? I thought the front up to the lower arm mounts, are basically the same. that is the only area I am worried about. using my winch time again and the stress on the steering box gives me reason enough to stiffen. if anyone has used xj stiffeners in the front, please let me know

 

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XJ and MJ front stiffeners are the same, the mid stiffeners back are different.

 

Basically anything past the cab support under the door will be completely different.

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