The differential cover is rotted out and leaking even though the rest of the truck is not. Is there any way to have ford fix this as a defect in materials and design.

I would understand if the vehicle was all rusty and this went bad, but for a 2007 to have one rot out this quick seems like faulty metal was used.

 

I would doubt that Ford is going cover a diff cover on a truck that is 8 years old. But couldn't hurt to try I guess.

 

I have never heard of that happening to any vehicle regardless of age. There has to be some environmental factor involved. I see you're in the 'rust belt' and lots of salt is used there in the winter. Maybe they did use some cheap steel in those at that time and the salt attacked it worse than the other parts. I don't drive mine on salty roads but I'm sure going to keep an eye on it! Whatever, now's your chance to get a fancy diff cover!