Water! Moisture got between the two pieces and made rust, the rust swelled to let more moisture in and made more rust. The factory only dipped the bodys in anticorrosion stuff up to top of the wheel tubs so any thing that gets even slightly damp above that gets pretty rusty :angry6:. It would have been nice if they would have dipped the whole body but then we wouldn't have so much fun fixing roof seams, window frames and trunk gutters then.
