I tried looking around for other topics to find this information, but I apologize if it's repetitive.

I'm planning out my next XJ build and want to figure out specifications for welding directly to the unibody.

basically saying, is it a steel or aluminum unibody and what sections are the thickest gauge to weld directly to?

 

All steel. The thickest bits are the framerails. What gauge i have no idea. The body uses a thinner gauge, probably in the 20-18 gauge range, but because the panels are spotwelded to each other, the overall thickness varies in places. IIRC, the hatch is metal for 97-01, and fiberglass before that.

What are you installing?

 

Listen to this guy.

As for my 2 cents - replacement body panels typically come in 18 gauge if that says anything, and the framerails are supposedly 16 gauge or thereabouts (it also supposedly differs in thickness by location).

And yes, metal hatches are 97-01, anything before is fiberglass. Source: own a 1989 and they changed nothing body-wise until 97

If you're going to be putting any weight on the body panels you will need to add additional strengthening/gusseting first to ensure they don't warp.

Edit: It seems that nobody likes to agree about anything regarding framerail thickness. People say anything from 10-16 gauge, just assume it's on the thinner side of that spectrum so you don't go overloading things.

 

Yeah, listen to these guys.....
Cuz I dont know

 

 

You have to turn the heat down, but you can weld to it. I plated my frame with 3/16" steel and welded it directly to the uniframe

 

It's metal, you can weld it. Not sure about turning the heat down, because the entire structure is one big heat sink. If you're getting a good weld though, adjust it however it works for you.

 

Dunno the gauge for sure, but I'd guess 14 or 12 in the rear. I had to cut mine out due to rust and spliced in a section from a donor vehicle. Welded 1/8" plate as reinforcements at the joins.