Ford Repair: Ford Expedition wont disengage 4wd, litre v8, vacuum system

Question
I have a 98 expedtion 5.4 litre v8 i have replaced the shift motor and selector switch it still will not disengage four wheel drive unless shift motor is unplugged there is no vacuum system for its four wheel drive it is all electronic in the transfer case it is supposed to be all wheel drive or four wheel drive

Answer
Have you taken this to a dealer to have the vehicle scanned. This vehicle and the year was known for problems with the " G.E.M. " module which controls the 4x4.. That unfortunatley is going to be my first suggestion as i'm prety confident that is where your problem lies.