Drip Rail Rust

[Bob B.]

Here on the west coast, about the only rust I see is in the rockers, kick panels, and doors, usually caused by plugged drain holes. I have seen trucks from other parts of the country with bad rust in the drip rails and both the inner and outer roof. I have a friend that currently has a '70 short step with rust in those places. We have a good roof and are probably going to just change the whole thing. My question is how does rust in the drip rails and roof usually start? I was thinking it is caused by water between the inner and outer roof, maybe due to a roof antenna or cab lights not properly sealed. I have seen trucks with the drip rail cauking in really bad shape but no rust under it.