Rear Frame repair

A few weeks ago my jeep stoped running and I had to drop the tank. It turned out the fuel sending unit had a broken hose on it (thanks again old man). Anyway, when I removed the gastank I took off the shield for the fuel hose that runs from the filler neck to the gas tank. Because the shield only had one small drain hole (which got pluged with mud) it acted to trap water and salt against the frame. The frame rusted out from where the cut out is for the fuel lines almost to the rear spring shackle (the hole is about 15 inches long on the inside of the rail, with a 4 inch hole on the outside). My question is, has anyone had to do any simular repairs to their XJ, and what type of metal I should use (specifically I wanted to know the thickness, because I might be able to getsome steel channel that could be close in size to the origional frame.

The XJ's frame rails are about 1/8" thick or less in some areas. I found the best luck welding patches that are about 1/8" to 3/16" thick using a low heat setting on a MIG machine to try and prevent burn through. Be sure to clean the area very well. I've had the best results welding by building the weld puddle on the good new patch metal and weaving it onto the frame rail metal.

It's also good to drill a bunch of holes in your patch and plug weld it to the frame as well. This will help the old frame apply loads more evenly to the patch and hopefully reduce the chance of fatigue at the perimeter welds.

Thanks, that advice is going to be a big help, I'm not the one who's going to be welding (I couldn't even get the mig to do my floor) but I'll pass it on to the guy who is.

all of the unibody is 14g, the front area around the transfercase is 2 layers of 14g, as far as fixing it, cut till you find good metal, and weld some new 14g to it, if you want to start stiffening your unibody, plate it w/ 3/16"