I have a 2002 f250 super duty v10 with the manual transmission... it has aloud squeak from under the truck when Im slowing down or maintaining a certain speed. The squeak goes away when I accelerate or if I push the clutch in. It does have a vibration to it when im speeding up. And shakes bad sometimes when I let off the clutch from a stop

 

Sounds stupid I know, but grease your tailgate latches. I thought my truck was squeaking and I could not figure out where from. My brother took my truck for the day and told me that his squeaked like that and he just greased the latches and it went away... well sure enough it is quiet now.