2006 F150 Auto Trans issue?
 

On my way home yesterday, My truck started rattling from below very loud while i was travelling around 70mph. i exited the freeway and when the truck came to a stop i felt two clunks from underneath and the rattle went away. I continued home and took it out later last night and it wouldn't do it anymore. It almost sounded like the 4x4 was trying to engage. I tested the 4x4 switch up and down my street and it worked fine. Has anyone else experienced this? My truck is out of warrenty and i at least want to have a starting point of conversation with the service people when i call. Thanks for all your help.