Has anyone installed frame stiffeners on their xj?

I’m pretty my unibody/frame frame has been compromised in the rear. I’ve purchased IRO frame stiffeners but wanted to see if anyone on here has installed them before I start the process.

other than this modification, my xj is bone stock.

Never!
If your uniframe is rotted away it'll be hard to weld to nothing.

Yep ya have to have something to weld to. holes can be patched, but ya need to see how bad things are under the jeep.

There’s zero rust on my xj. However the previous owner attempted to pull a stump with it and shattered the planetary gear in the transfer case. I’m guessing that he broke a few welds along the unibody/frame and as a result I get this wierd clunking from the rear. I’ve replaced the following to try to address the noise.

rear leaf springs, hangars and bolts, sway bar bushings and links, shocks and exhaust hangers, u-joints throughout, motor and trans mounts, rebuilt the rear brakes, rear axle bearings and seals.

Post some pictures of the rear of the uniframe and i'm sure we can help tell you if there are any defects. I did the rear of my Jeep with HD Offroad stiffeners and was done within an hour. Remove the wheels, clamp the stiffener down to the uniframe, mark where you'll need to buff the metal clean to weld, clean everything for welding, clamp back up and go to town. I recommend either removing the gas tank or being cautious and liberally cover it with heat resistant material like an extra welding glove around the funnel tubes. Also don't forget to disconnect the Jeep's battery.

I had a friend of mine ride in the back and he said that it sounded like the body panes were popping. I originally thought that it was the leaf spring moving around in their mounting pockets and it still may be but the sound almost seems to be coming from the drivers side rear, maybe near the gas fill... Im at a loss. I took it to a suspension/alignment place after I replaced all fo the front end stuff (coil springs, tierod and ends, track bar and sway bar and links) they said that they had no idea what the clunking sound was.

Your body/frame sure looks like it's in about as good condition as it can get! If you're stock...don't risk future rust by welding on frame stiffeners and removing the nearly immaculate rust preventative costing you've got on there.

Clunking could be shocks...worn out bushings are plentiful on the bar pins...and it can get insanely loud/annoying. Just replaced mine, and it was amazing how quiet it got again.

Lots of other potential causes...but based solely on your photos...don't do stiffeners!

my mistake, patman, when you said compromised I had assumed rusted out. Our ford escape clunks at bumps due to a busted exhaust mount, we fix it every year. does the clunking happen at low speeds? if so have somebody walk beside/behind the jeep while hitting bumps, maybe they could pin point the noise. you can also look for bare metal under the jeep, should be an indication of were something is hitting. hope this helps dt

The body's have at least a little flex in them when they were fresh off the assembly line. Have you tried checking for rub spots behind the plastic interior panels yet ? If there are any a little friction tape oh stick felt will quiet that right now. Are all the panel screws tight ?

To add to this, if you have access to a GoPro or something like that, mount it to the underbody and go for a drive where you know it will happen and then look at the footage? Might take a few different places but could give you an idea of what area the noise is coming from, and you might even see something funky!

So after talking to a body’s shop, I was gonna have them put it on a rack to see if the frame was bent or anything. THey looked at it and said it looked fine. They didn’t even put it on the rack. So yea, the frame looks great. That still leaves me with a knocking that I cant sort out. Today Im gonna drop the fuel tank ( I need to replace the fuel pump anyways) but I figure that if I can drop that, I might see if the rear pan for the “bed” is dented, which may be enough to cause the clunking sound. I’ll let ya’ll know how it goes. I also have to replace my internal axle seals today too so it’ll be a fun day in the carport. Thanks for all the feedback guys.

A very common clunk sound in our XJ's can come from the rear drive shaft splines. I greased mine up with anti-seize and the clunk went away. As mentioned before, loose rear upper shock mounts can do it too.

Ok so I’ve replaced the fuel pump and the last exhaust hanger in the rear, over the axle, I also replaced the rubber fuel lines around the tank as well. I did remove the driveshaft and lubed it up well with anti-seize but the clunk is still there. I still have to add a washer between the leaf spring/bushing and the spring mount on the uniframe. Maybe the spring is popping back and forth in there. There seems to be about a 1/4 or 1/8in between the actual spring bushing and the pocket it bolts into. I did get the frame stiffeners in the mail the other day and I have buddy that will be putting them on for/with me. Not sure what else to look for. Not that it matters but I also replaced all of my coolant lines and my inner axle seals on the front axle.

Took my wife and dog on a test ride. Noticed a mud puddle that I Simply could not resist. Well, keeping in mind that I live in the high dessert and we dont get much rain out this way. Well, I didnt think that 4wd would be needed and I was wrong. I got burried to my rear axle. After putting it in 4wd, I sunk the front axle too. Im so proud of my wife. She didnt say I told you so, not even one time. Thankfully, someone pulled me out withn just a few minutes. A little embarrassing but I sure learned a lot...