Another possibility is with the 4x4 system
IIRC, Ford uses vacuum in stead of solenoids for the hubs and they don't always release nor engage, depending on the issues. Buddy had his fixed via a TSB. Rain water from the cowl washes over the vacuum control & motor. Messes it up and then the water runs down the vacuum line to mess up the hub gear set. Mostly they will stick and some times partially stick...that is what got him into the dealer for a 'ratcheting' sound coming from his right wheel...his hub gear was stuck in-between engaged and disengaged
IIRC, Ford also uses a computer module to control the transfer case and motors to shift the transfercase.
I'm old school and dislike all of these computer controlled and motorized shift linkages. Prefer the levers that confused too many and they why the OEMs have gone to automated 4x4 controls
Also, do you drive with the 4x4 in lock while on pavement? If so, your 4x4 system might be binding and that is holding it back until it unwinds. If you, don't, as it will ruin your 4x4 system