I just got an '06 that's beautiful up top, but looks like the pits of hell underneath. This truck came from Ohio and I'm in Florida. The only way we could come close to this type of damage is to drive it into the bay on purpose and leave it there for a few months. Needless to say, nobody does that so we have no method to stop the damage before it gets worse. What does everyone up North do? Do you just watch a truck rot away? Someone suggested spraying the entire underside with transmission fluid?