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Possible to repair unibody frame rails?

jeepxj2007

NAXJA Forum User
Location
Michigan
Hello, Is it possible to repair a unibody frame rail?...Like if it rots out in a section? Can this sort of thing be cut out, patched and welded in? Or is the hole thing junked? Just a thing I've been wondering about the last few days, thanks!
 
It depends on how big of a section and the overall state of rust on the vehicle? Pics may help here. Have you taken a punch and tapped other sections of the rails to check the strength? I have had floor pans that looked great underneath and were 80% gone on the inside. Allways found this by hitting the floor in different spots until the punch found a weak spot. Went topside pulled carpet and all the nasty stuff was revealed.
 
The frame rails aren't rotting, Im just looking into the future, i Had rot under the passenger rear seat floor boards, (in the compartment where teh jack is and what not right above the muffler, it rotted through the floor, i cut it all out, but the top of the frame rail all the floor board was gone, but the frame rails are still intact and completelty solid,they have surface rust, but im just looking in future terms, woudl it be possible to get this patched or boxed in the future if the rail did rot here, this is the only spot i have rot on the whole underbody,i patched the holes i cut out with stainless sheet metal and caulked it, and painted over the surface rust with rustoleum...so hopefully it stops and doesn't spread...how much would something like that run.... i know i wont get a exact number but about how much? it is a 89, i really woudln't care, but the whole drivetrain has less than 50,000 miles
 
From my experience the floor boards rot out LONG before anything else. I woudlnt be too worried about it. But yes, technically if you wanted to patch up the Unibody you could. But again, if its still solid now, I wouldnt be too worried about it, the floor boards have a tendency to rot out (I have a 93 and by the sounds of it it is far worse than yours).
 
attack the rust now and stop the spread and you'll never have to worry about it
 
I wouldn't worry too much about the frame rails rotting, but I do recall that some forum member or user a while ago posted from somewhere in the Canadian Maritime Provinces with a report of replacing a very large section of rotted frame, and I think he was successful. It was a lot of work, though. I've seen some awfully rotten XJ's, including my sad and sorry 95, with no visible frame rail problems despite floor to ceiling rust everywhere else.
 
My floors are rotted something terrible,like yours under the rear seat is really bad. The frame rails are rusted too, but its only surface rust. I am sandblasting them and putting two coats of Zero Rust on them as I go.
When the pans are fixed I will coat the int/ext with a couple of coats of bedliner.
The frame rails are the least of my worries.When I started removing the front floor pan today I expected to find the rails in a serious state, to my surprise the pass. side rails were in great shape, a little rust on a couple of bolts , but other than that they are pristine.
The rear rails are in bad shape but salvageable. Had to air chisel my rear bumper off, including the bolts welded to the rear crossmember. I managed to crack one of the rails in the process, but drilled a small hole at the end of the crack and then welded the crack and welded the rail all around where it was spot welded to the rear member, its good now.
 
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