1998 Expedition won't shift into four wheel drive replaced sensor and switch on dash still doesn't work any suggestions?

Answer 1

Ford uses a vacuum motor to activate the 4WD, if your vehicle says it is going into AWD, but not 4WD then it is likely the Vacuum motor. AWD doesn't actually do anything if the vacuum motor is busted. Vacuum motors are a crappy way to shift an axle into 4WD, they are very prone to failure. I had one in my Jeep that I replaced with a cable actuaded system. Posi-Lok makes some systems, not sure if they make one for the expedition, but I am sure it could be adapted to work. You can build your own cable system for about $20 if you are handy with some basic garage tools, and understand how the system works. I would start by pulling your Central Axle Disconnect (CAD) off the fron axle and check the shift fork, make sure that is working good and has all the parts, then check the vacuum hoses that connect to the CAD, have someone shift from 2WD to 4WD and make sure pressure is comming through one of the hoses. If you are getting preassure then your system is working properly and it is probably just an electrical issue, if you are not getting preassure then you could have a bad vacuum motor, or broken/cracked air lines, or a disconnected air line, or a disconnected vacuum motor. Either way the vacuum systems are not reliable and even if it is a simple fix (reconnecting a vacuum line) I would recommend you look into replacing it with a mechanical system. Just my $.02 Good luck Not sure what this guy is talking about,,The question simply needs more detail. If your trasfer case is not shifting from 2x to 4xhigh or 4xlow I would check the "electric" motor on the transfer case, only (2) bolt hold it in. Take it off and have a trusty friend try to change to 4x, be carefull and put it back the same way it came off. There is a worm type gear that goes from the "electric" motor to a gear selection module, this gear may be gumed up or stuck. If you have driven thru lots of deep water I would suspect this gear is stuck. The "electric" motors will also sometimes go out but rarely. Good luck