ooh boy; I saw scale inside my frame, going up past the holes in the sidewalls of the frame right behind where the running board mount is; you can stick your finger in and feel the buildup;
The way I discovered really how bad mine was, a couple ways.
Back in about '06, I had to have a new cat put on; the exh shop pulled the skidplate and spun the rivet nuts within the frame when they pulled it; I had put the 1st clutch in this thing in like 04, and anti seized all the bolts, so I was quite surprised. All 3 on one side and one on the other did this; the ex shop wound up cutting the heads off some 1/2" bolts and welding them on so that they could put nuts on to hold my skidplate/cross member back on. Lots of comments back then along the lines of "HOW old is this thing"? they could not believe it and directed me back to the dealer to check on the possibility of a recall from it; "bad batch" of steel possibly.... I came up empty there.
Then I got hurt in Sept 07 and had to park the Jeep; as it sat I pulled the wheel well flares and running boards to get them painted; I went to pull the back mount on the driver side and got a huce chunk of metal with one of the bolts; I wound up cutting a larger hole into the frame so I could get a 1-1/4" shop vac hose inside and beat on the outside of the frame with a ball pein to jar everything possible, loose from the innards so I could vacuum it out; my thoughts were that that scale could be doing no good, all it would do would be to hold moisture like a sponge and speed up the rust process; so I figured I had to get it out; so when I got as much out as possible I cut a patch and welded it into the frame and ground it smooth; I cut a hole in the same spot on the pass. side and did the vacuum treatment; that side was less than half-as-bad.
Well since the Dr still said I could not drive a stick, it sat.
I went to get it out in Spring of '09, and when I went to reinstall the running boards, I gave the whole frame a once over and found another soft spot on the driver side, so I decided, that was "it"; I would locate another frame if I had to buy one from one of these aftermarket companies that builds stronger ones for hard core off road; I'd found a couple for $1200-1500.
Meanwhile I kept an eye on Ebay and C-List and found one about 80 miles away on C list. So I went and got it, completely stripped the orig frame bare and reassembled everything to the new frame.
My son was about to get his licens for the 1st time, and knowing that having driven myself for 25 years at that point, that i may not be able to handle it if the frame went (hard telling exactly "when" something like that would "go", I sure didn't want my zero experience son in it when it went either.
Knowing that w/a bad frame it was basically worth "nothing" to sell, and that I had had it for 9 years at that point and that it remains THE most expensive vehicle I have ever bought, the engine and remaining drive train had only about 83K miles at that point, and I had no idea if my "next one" might have the same issues, I decided to spend about 2 weeks in my garage and lift the body off, dismantle the whole thing and reassemble it to the new frame.
I'm certainly glad I did it. I had some other things going on, I could not work "constantly" on the swap. If I could have it would not have been a 2 week process.
and then the 1st time out driving it in 18 months, I managed to run into an a-whole cop that decided to sting me w/a speeding ticket; on the way to pick up temporary insurance cards from my agent, no less, since I just re instated it like 2 hours before, that morning over the phone.......
