Quote:
Originally Posted by daveb
Looks like both cracks started on a spot weld. Body shop isn't that worried about it but attribute both due to body flex. They didn't come out and say it was the top being cut out as the root cause but said there is more flex due to the doorways. The window guy also told me the van front windows flex more than most vehicles. They plan to reinforce both areas but also warned more spots might pop up where no backing is.
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To me it's clear these two cracks are related to same body flex, and also agree that cutting out a large part of the roof doesn't help matters because it allows the body to flex more and concentrate stresses in areas that were not designed for it.
The roof acts as a diaphragm which makes the body a lot stiffer, particularly in torsion (although stiffness isn't necessarily always a good thing). And the body man is absolutely correct that the side doorways don't help either. On the driver's side the continuous side body panel also serves as a diaphragm to limit twist, so when the body has to twist due to off-roading, movement or flex is concentrated where the body is least stiff -- and that's the passenger side.
Although it's hard to tell from pictures, it appears to me that both cracks are related from body flex in the same direction. That is, twisting the body caused the roof area to move back relative to floor (as in shear), which then caused these two areas to fail due to the areas being placed in bending.
And if both started at welds, it's somewhat likely that cracks started due to many load cycles leading to fatigue. I'd expect a one-time large event to fail different.