Good thing I didn't make a useless response, like maybe it's a dog peeing on your truck

 

Tiamat-
Yeah, I saw the underbody spray everywhere. It was from the rear of the fuel tank back. The rear of the fuel tank, spare tire, and basically every other surface under my truck had (and now has, again) spray marks on 'em. There was no oil or residue on my driveshaft (I thought maybe it was running down from the transmission and being slung everywhere), nor on the bottom of my diff. It's like it's in the early stages of leaking and is only misting...not full-on driping, yet. I'll dig around and see if I can find the old pics of my tailgate. The spots are really fine and you don't notice 'em until the truck gets dusty (I go to a buddy's farm every now and again and they REALLY show up afterwards).

 

DUCK01
There is a breather on top of your diff. See if anything is coming out of there. See if there is any residue on the breather. Does it seem to be rear end fluid?

 

On a side note, this board has the absolute BEST search engine I've ever used. GREAT job Staff!

Anyway, here are some of my old threads and pics. The first link is the one of the pics of my tailgate. The second link is a detailed description of what's going on under my truck.
https://www.f150online.com/forums/sh...light=tailgate
https://www.f150online.com/forums/sh...light=tailgate

 

Saw your pics. My truck never got that bad. Have no idea if whats up with yours.

 

Yeah, me either. Thanks for the help, though. It's back to that point again, so I need to do something before I road trip in a few weeks. It's just odd, though, because NONE of my fluids are low. It seems that if I were losing that much of something, I'd surely notice after a few weeks.

 

Take it to the dealer before your trip. Hopefully they will find it.