First time making a new thread on here so bare with me! To those whom may have a mystery squeak on an '04-'08 F150 that seems to never be found, it could be your tailgate latch! My father owns an '05 King Ranch, which was bought brand new, that has had a rattle pretty much since the day he bought it. Brought it back to Ford to fix and they messed with the power rear glass, the rear seats and all it never resolved any of it. He gave up and its only gotten worse and more annoying to him. I drove over to my parents house to drive him to the airport at 3:30am and dropped the tailgate to put his luggage in the bed of his truck (too cheap to drive my own) and closed it. I happened to pull on the tailgate and noticed the noise that he's been hearing for the past 5-10 years! didnt say anything, drove him to the airport and got back to their house and i started pulling/pushing on the tailgate and isolated it to the passenger side tailgate latch. Grabbed some WD-40 out of the toolbox in my truck and the noise disappeared. Countless hours of an annoying squeak and multiple times taking it to Ford was resolved with $.05 worth of oil. Sorry for the long post!! I felt the need to emphasize and ellaborate that the small things can make for a large/annoying issue.

 

Glad I'm not the only one who's had the tailgate squeak.

 

Good find, and thanks for taking the time to post it!
Another way to fix these squeeks once found is to use some white grease (can buy it in a spray can with the red tube to pin point the application); it will last longer then the WD-40, especially in outside conditions subject to weather conditions that can wash away WD-40.

 

I normally use white lithium but for all intensive purposes i used WD since its what I had on hand.