FWIW, I was climbing around my SD & discovered rust in the lower part of the doors hidden by the door seal. I never would have seen it unless the doors were open & I was looking from below. Glad I found it before doors need to be replaced. Strangely, only the fronts are affected - primarily the passenger side. I can't account for it as the drains are clear.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.