Hutch,
I don't know who makes the frames, other than it wasn't Sunline. The tire wear part sounds like a bent axle, but the battery tray thing threw me. I spoke with a cargo trailer dealer a few months back and they said bent trailer axles are more common than you think, especially on Michigan roads. Now that I think about it, I had something going on with the 2363, because the left rear tire was worn down (to the point where metal pieces were sticking out) when I got it. I found this a little odd because one tire shouldn't normally wear this much. I figured they were original tires and were just old. Upon further inspection, the tires were newer (the previous owners said they replaced them, but you never know) because they lacked the scuff band around the sidewall like the older model Goodyear's had. I ended up swapping the tires and wheels from that to the 2251, and vise versa, because I had painted the other set of wheels. I had the one bad tire replaced and figured all problems were solved...Right? Well, I noticed the left rear tire now (original Goodyear's from '94) on the 2363 started showing a little wear. I didn't put many miles on that one, but I saw the start of it, and it didn't happen when those were on the 2251.
The moral of the story: I'm guessing the axle was slightly bent, but I didn't keep it long enough to find out.
Also, my dad's car hauler has a problem where the spring mounts are a little off center. It causes some inside fender rubbing, but not enough to justify pulling everything off and re-welding.
I'm surprised about the crack. My only suggestion for this is faulty metal.
Even though I wouldn't rule out the crack as a reason for the front crossmember/batt. tray bowing up, it sounds like whatever hitch was used was too tight, and therefore put a lot of stress on the frame. I'd need more details as to what type of hitch, what weight ratings the spring bars have, etc., in order to make an educated decision if that could be at fault.
I'd also be curious to know where exactly this crack is at. Is it in a crossmember, in the rails themselves, or near the axles?
Jon
P.S. If Nelsoje doesn't come over here, feel free to post this over on the Open Roads Forum.