Wonder why this is?

[mudpaws]

On my '86 FJ60, the rear rails are "blistering" at the spot where a lot of these trucks tend to rot (between the aft end of the wheel arch and the rear shackle mounting point). You guys know, the way the two "C"-shaped frame rail parts (two sandwiched "C"s if you cut a cross-section out) start to separate from one another. Anyway, where I'm headed with this is why did this happen? Inferior metal? Lack of undercoating? This truck spent its life being garaged and aside from a little outer quarter rot, there is no rust at all on this rig. I just think it's weird how the frame isn't mint, or at least better than the body shell. Further, that part of the frame is OPEN, not a place where water or salt builds up. Any input from anyone? I guess with the extremes in temp we have here, and the humidity, salt roads...Anyone?

Thanks
Paws

 

[hammer1]

you nailed it. salt on the roads, and humidity/salt air.
my 84 is like you described.
every year, i wire-brush and then treat what i can, especially inside the frame
eventually, the rust will win.

 

[mudpaws]

Yo hammer! Yeah man, I want to do something about it soon. It's actually next to nothing in the scheme of things, and how tough these frames are- but still. I'm a perfectionist, so I was thinking of how to make a repair of this as exacting to stock as I can. I saw that Auto Rust place in RI, and I was thinking- My bro's friend is a bad ass welder, and I can fabricate a bit (not weld)so maybe~ I can take my time and cut/grind out the area(s). They are not huge, so I possibly can (elbow grease here) work on them and make the exact shape/gauge steel plates and have Jay weld them in for me. I'll try to post some pictures of the areas soon. Maybe 'box' the frame there? Just for total toughness!