Installed a 3in rough country series 2 lift in my 2000 jeep xj. I then went to put in my transfer case drop bushings. Front studs came out fine and new hardware went In even easier. Then moved to the back bolts to find that whoever owned this jeep before me had put some sort of large self tapping screws into the frame and messed up the treads. I then cut into the frame to drop the bolts though the top and came to my 2nd problem. There was some sort of hard styrofoam stuff in the frame and a piece of metal covering the bolt holes. I have no clue what it was for but it makes dropping bolts through the holes impossible. So this is my next attempt. Weld a piece of square tubing to the frame and put nuts inside the square tubing so that I can tread bolts into it. What gage square tubing should I use? And will a welding shop be able to do this? Or my buddie down the road who works on race car frames? Does this seem like the best solution? Will it be strong enough?

 

Why do you want to use a transfer case drop is it that you don't want to change the rear drive shaft ?

 

I ran into similar with mine. My bolts broke off so i used a small hole saw to make access holes where you did. The foam stuff is factory for what ever reason. Now that you have the holes cut in the side of the frame reach in with a hammer and punch and knock the factory welded in nuts out. Slip a new nut inside the frame, a bolt up through the hole, and crank down on it to flatten out the section inside the frame where the nut sits. Take out the nut/bolt and clean out whatever debris or foam in around where you want the nut to sit. Now get bolts long enough to go up through the crossmember and the square tube you made. Put new nuts if you buggered them up flattening out the inside of the frame. Nylocks are recomended. No welding necessary.

 

Take it to a local fab shop, with a case of beer and I'll bet they'd do it up