Overfilling the tank risks damaging the EVAP system in your truck. The EVAP (or evaporative emissions system) is designed to prevent raw fuel VAPORS from escaping the gas tank and fueling system to the atmosphere. The EVAP system captures these vapors, and holds them until the ECM determines it can purge the vapors through the engine to be burned. But, by overfilling the tank, LIQUID fuel can be sucked into the system and damage the valves, sensors, and charcoal filter media used by the system. The system can tolerate a certain amount of liquid fuel, but, if you regularly overfill the system, it can get overwhelmed and give you DTC codes. And, with today’s cars, most of these components are expensive.
Also, for the Expedition, the system may already have some damage. The EVAP system on your truck and as part of the gas nozzle for the station are suppose to work together to prevent fumes from escaping. But, if either system has problems, yours or the stations, the fuel nozzle can ‘click’ off before filling the tank all the way. That rubber cup or boot on the nozzle is designed to create a seal to prevent fumes from escaping. But, if the system is not venting correctly, it will cause the tank to pressurize. I have a similar problem with my Ford Explorer, and the only solution has been to pull the nozzle out an inch or two from the filler neck to allow the pressure inside the tank and nozzle to equalize. Then, I can fill it all the way, and it will still click once full.