Are 2005 and later Dakotas prone to rust underneath? My 2007 is very rusty underneath: frame, rear axle, springs, sway bars, front suspension components... I have had the pickup 4 months and it was a one owner with 12000 actual miles and a clean Carfax. I talked to the prior owner recently and he claimed the truck was hardly ever driven in the snow but it was always kept outside. None of the body panels show rust underneath or outside.

 

Is it just surface rust? Possibly dirt? That would be fairly normal for a vehicle stored outside.

 

Iron, water, oxygen => RUST

It is normal for the steel below the beltline to get rusty. Any coating gets quickly sanded off from normal use and then nature takes over. The natural order is return to dust.
The right amount of rust actually will protect the steel below (for a while). You are lucky that the rear fenders aren't rusting out. That's the next thing to go.

 

I really need to get it up on a lift and see how bad it is.

 

I know this thread is almost 7 months old, but I want to post some follow up. I have been underneath the truck some more, and it is really rusty. I mean really. I told the wife that we don't have to worry about it wearing out, it will rust out first. Exterior is still mostly rust free except in a few places: the bottoms of both of the rear doors are bad. Not showing through the outside yet... Still runs and drives great!

 

Why dont you have something like Fluid Film sprayed on the bottom to at least slow the rust down. Its kind of stinky for a day or two after you put it on so l would not put it in the garage right away. Just did mine with the stuff. Got the recommended spray gun and about 90lbs air pressure and it went on like paint. Pretty easy actually. Not sure if it really works,but I wanted to try something with mine.