I'm going to get the frame fixed. My dad knows a guy that is a retired railroad welder; he did some repairs to my dad's frame and plow plates. Have an appointment with him next week; might have to take the box off for him.
I honestly don't know what caused the break, but I'm almost certain it just happened yesterday. I'd like to think that I would've noticed sooner if it had broken! When I had the truck in for MVI in October the tech that did it said the frame was looking a little weak in some spots. It has been patched before in the rear; the crossmember for the spare tire is not there anymore. In its place is a piece of square tubing. At some point I would love to piece in a rust-free frame section from the cab back but getting one of those in these parts is going to be difficult.
And yes, I haven't had much luck with my trucks. My last GMT400 was wrecked in a crash, and my previous trucks (all Fords) had things wrong with them. I chalk that up to my habits of buying vehicles, that is buying cheap ones to fix up that end up needing too much work. I had a 96 F-150 that was I would say the second best truck I've owned (first being this one) but it was only a 2WD. Life lessons...!