i have changed battery and alternator in my 2004 ford expedition and truck stars and runs fine for just a few min then my battery guage drops and truck will shut off whats the problem
Sounds like the anti-theft system is active, have you tried the disarm procedure in the owners manual?
Yes I have done that already
Then your other option is tow it to a dealer and have the system reflashed. When the battery was disconnected the power was gone too long and the capacitors discharged so you lost all of the factory presets, so the only way to get them back is to have it flashed to your VIN. there is a tool that plugs into the power port that has a 9 volt battery that keeps the presets alive when a battery is removed, there is also a fancier one that plugs directly into the OBD2 port and uses a jump box for power, much longer battery life one this one so if the repairs take longer than expected your covered. HTH
Check for blown alternator fuse.