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Floor welding/Repair


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My 87's floor has seen better days. The previous owner just let them rot then covered them in Plywood :thwak: I ordered new floor pans from C2C but I have never tried to replace an entire pan before only patching holes. I cut out all the crappy rotted rusted floor from the cab but this left me with very little to weld to near the door. Anyway...to questions, will my 110flux welder suffice for an entire pan? It did great on patches but this is a bit more of a project and is it okay to pop rivet the floor pan in place then weld it? or should I avoid the mighty rivet all together?

 

 

Here is my floor the day I got the truck for referencing (Before cutting the rust away)

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It all matters how high the damage goes on the tunnel to how much work you really need to do. My rot was basically everything in front of the rib on the floor pan on the drivers side plus up the tunnel to the top bolts of the transfer case linkage bracket, and the front left corner on the drivers side.

 

What I ended up doing was buying a full OEM Cherokee front floor pan. My buddy is a body guy so I got him to come over and give me a hand. What we ended up doing was cleaning most of the rust area, cleaned up the edges, primed it, then Por15'd the whole floor (only primed since I had to wait a few days for the Por15 to get in). he ended up cutting the Cherokee floor in half (so we can get it in the door easier), measured to the rails, then cut it to fit between the rails. After that we just patched the rest of it with the extra metal from the floor that was spare. Once everything was in place, we laid down some liquid nail and are letting that dry right now. he'll be back tomorrow to tack weld it together and weld from underneath the area that is rotted through to the new floor to create a nice seam (he knows how I go wheeling so we're trying to make this as waterproof as we can).

 

This is still a work in progress (finishing it up next weekend), but the drivers side we will have to lay the panel in, then weld in another good sized piece of steel to reinforce the top of the frame.

 

You will also want to do that last part since the top part of your frame rail rusted away. This will strengthen the frame back up by fully boxing the frame rail again (the 16 gauge, or whatever it is, steel for the floor pans will not do anything if you get into an accident. As my friend said, it can fold like an accordion if you get into an accident).

 

If it is not rusted up into the tunnel area (from the looks of it, it is rusted up into that area), you can get away with just picking up a Comanche floor panel. If you do this, I still highly suggest putting that extra piece of metal in there for the ribbing to strengthen up the frame back to factory specs.

 

I was pretty much just being his tool fetcher as he did the work but I kept a close eye to learn. It actually is very easy. You will definately want to get some seam sealer (we're using Locktite's version of liquid nail which should do nicely).

 

I'm going to be snapping some pictures of what we've done so far and after he tacks this side together to put on a build thread I'm doing on another site, I can post some of them up here if you would like.

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This is still a work in progress (finishing it up next weekend), but the drivers side we will have to lay the panel in, then weld in another good sized piece of steel to reinforce the top of the frame.

 

You will also want to do that last part since the top part of your frame rail rusted away. This will strengthen the frame back up by fully boxing the frame rail again (the 16 gauge, or whatever it is, steel for the floor pans will not do anything if you get into an accident. As my friend said, it can fold like an accordion if you get into an accident).

 

I've been debating this same issue on mine...

 

The top of my frame rail was rusted away too so I cut it all out. I have not been planning on putting anything back in its place after the new floor pans are in for a couple reasons.

 

(1) The replacement floor pans span completely accross the cab from the inside of the rocker to the trans tunnel thus regaining some of the strength lost from the removal of the top of the frame rail. The factory set up just has floor pan on either side of the frame rail and then the boxed in top over the frame.

 

(2) The boxed in top portion of the frame rail may be thicker metal than the 16 ga. floor pan, but it sure isn't by much if it is.

 

(3) To my knowledge, the XJ does not have the boxed in top portion of the frame and just has floor pan straight across. If the MJ would smash like an accordian in an accident without the top boxed in frame rail, wouldn't we be seeing this problem with cracked up XJ's.

 

(4) Anything that is done couldn't be any worse than the rotted out frame rail that is there.

 

...I could be off on some of this, so if there is someone out there with more experience, please fell free to enlighten me.

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(3) To my knowledge, the XJ does not have the boxed in top portion of the frame and just has floor pan straight across. If the MJ would smash like an accordian in an accident without the top boxed in frame rail, wouldn't we be seeing this problem with cracked up XJ's.

 

The XJ's actually had horrible crash test ratings due to the rocker in the middle caving up. Unfortinately I don't have the crash test video anymore, but it crumpled in the middle of the rocker and in the roof right above the driver in a drivers side front corner crash.

 

The metal above the floor that was used for reinforcements is a lot thicker than the floor pan itself, two or three times as thick. If you look inside the hole, you'll actually see the stock floor pan in there with the reinforcements welded on top. These hav all been pinch welded together in many spots to create as close to a solid piece as they can. The floor pan, itself, on top will not net you any real gain of structual integretiy of the rail as it's so thin, that will just create the weak point in your frame in an accident.

 

But yea, at this point, anything that you add will be a massive gain over what you have now.

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trim out the bad floors.

 

place new floor pan is. locate the lips for the frame rails. mark spots every 1" for the complete length of the lip on the frame rail (mark it into the new floor pan) and drill out those marks. there are two lips (flanges) per frame rail.

 

 

set the pan in, use a hammer to hold the pan down, and use your welder to start spot welding those holes down. THEN start going from center to corner on either side of the pan with spot welds until you get all the way aroundn the pan.

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(3) To my knowledge, the XJ does not have the boxed in top portion of the frame and just has floor pan straight across. If the MJ would smash like an accordian in an accident without the top boxed in frame rail, wouldn't we be seeing this problem with cracked up XJ's.

 

The XJ's actually had horrible crash test ratings due to the rocker in the middle caving up. Unfortinately I don't have the crash test video anymore, but it crumpled in the middle of the rocker and in the roof right above the driver in a drivers side front corner crash.

 

The metal above the floor that was used for reinforcements is a lot thicker than the floor pan itself, two or three times as thick. If you look inside the hole, you'll actually see the stock floor pan in there with the reinforcements welded on top. These hav all been pinch welded together in many spots to create as close to a solid piece as they can. The floor pan, itself, on top will not net you any real gain of structual integretiy of the rail as it's so thin, that will just create the weak point in your frame in an accident.

 

But yea, at this point, anything that you add will be a massive gain over what you have now.

 

I am unfamiliar with the crash test ratings for the XJ, however, I see where you are coming from about removing the top of the frame rail. I just compared my replacement pans with a piece of the old top of the frame that I cut out, and you are right it is about twice as thick.

 

Do you have any pictures of how you addressed this problem on yours when you welded your pans back in?... I'd be curious to see.

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My buddy and I did the easier of the two sides this weekend and prepped the other side. We're still trying to figure out what we want to do.

 

Since mine is only rotted out in a section about 8 inches long in a spot right in front of the side rib, we might just cut the rest of the front part out, trim the Cherokee floor to fit in there and then weld a nice sized piece of metal over the frame part to box it back up. If you can wait till next weekend, I can post up pics of all the repairs and give more info once we figure out what to do, then set it all in place and burn everything on.

 

I think there are a few crash tests of the Cherokee on YouTube but YouTube isn't loading for me right now. :(

 

I'll snap some pictures of what we did so far in the next day or two to give you a better idea where I started from and where I'm sitting at with what needed to be and what has been repaired so far.

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My buddy and I did the easier of the two sides this weekend and prepped the other side. We're still trying to figure out what we want to do.

 

Since mine is only rotted out in a section about 8 inches long in a spot right in front of the side rib, we might just cut the rest of the front part out, trim the Cherokee floor to fit in there and then weld a nice sized piece of metal over the frame part to box it back up. If you can wait till next weekend, I can post up pics of all the repairs and give more info once we figure out what to do, then set it all in place and burn everything on.

 

I think there are a few crash tests of the Cherokee on YouTube but YouTube isn't loading for me right now. :(

 

I'll snap some pictures of what we did so far in the next day or two to give you a better idea where I started from and where I'm sitting at with what needed to be and what has been repaired so far.

 

Sounds good... Here's what I've got going. You can see why I'm asking.

 

Driver Side:

 

Passenger Side:

 

For a more complete look check out my project thread... viewtopic.php?f=7&t=26205

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Wow, yea, I see where you're coming from now.

 

Your best bet would be to get a Cherokee floor pan, weld the whole thing in (minus about 8 inches or so in the end where it's longer than a Comanche's), then weld reinforcement plates on the top. I got lucky where I'm only missing like 8-10" on the drivers side, in front of that side rib. It doesn't look too bad on yours, though, since it's mainly the floor itself (no firewall, rocker, ect.. damage).

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