As I stated in my original post and once again before this post, I checked Ford Parts and could not locate the under body composite material guards or the corresponding parts. fusionff attached a link to a dealership parts list and I'm narrowing it down from that. The stud/bolt I'm referring to looks to be 3/8 or 7/16, so I'm going to pick up a washer and a couple of nuts at the hardware store and install. Hopefully the slight looseness of the passenger side under body cover is the source of my rattle.
Not really, you can change fluid. Ford recommends changing fluid at 150K for normal conditions. I thought it was 60K for severe service. Most folks don't recommend going over 60k including tranny engineers. But not a sealed or lifetime unit.
Interesting story - when the Lincoln LS came out in 99 there was no transmission dipstick so folks assumed that meant the tranny was sealed and you never had to check or change fluid. Not true - they simply ran out of room in the engine bay for the dipstick tube so they left it out. You still had to service it the same way but using a second hole to check the level instead of a dipstick - like a manual trans.