I'm new to this tech/spec stuff, but I have a 04 FX4 Supercab with 5.4L. Just wondering what kind of rear end I have and where on the truck I can find out. I just bought the truck used so I don't have the sticker info....
any help would be greatly apppreciated...

 

The axle itself is a 9.75" axle - there's a two character code on your door jamb sticker that indicates gear ratio (search around here, it's been decoded several times before), and the gear ratio itself is also on the toe tag on the differential itself, held on by one of the cover bolts.