Okay, I glanced under the truck over the right rear tire and can see some rust on the front of the rear axle.
I am scheduled to take it to Line-X — across the street from the dealership — on Monday, January 17th after Ford does my driveshaft recall work.
Line-X is applying a product called Valugard as an under carriage protectant against rust for $500. They are going to apply a chemical rust converter over the rusty axle areas prior to treatment. The service includes a fogging type application inside the door panels to protect from rust as well.
https://www.x-tremefinishes.com/valugard
I was told the treatment is guaranteed for 8 years. Anybody have any experience with this?