While driving, four wheel drive quit working. It

Check and make sure it didn't blow a fuse. If it blows it won't allow it to do anything.

it sounds like the front differential is not engaging, check the solenoid on front diff.

This happens on these two to four wheel drive units, you need to get it to a garage that knows how to unlock or disengage the four wheel drive , doing this on your own will cause more damage.

hi
yes seems like you switch is faulty.]
replace the switch
Thanks

It's most likely the "four wheel drive actuator" This is located on the front differential housing. It's cylindrical shaped and has a large hex (about
1-1/4") and two wires coming out of it. Usually they short out and blow the fuse but, I've also seen where they just quit working and sometimes they just get slow to work. The "actuator" has a heating element in it and it warms up, some sort gas, causing it to expand thus engaging the front wheels. In cold weather it may take a minute or so for it to engage, so put in four wheel drive and wait for a bit and see what happens.

I had/have both of these problems with my '92 Explorer. They were unrelated. My overdrive problem
required a transmission rebuild. My four wheel drive not working is apparently a problem with the
computer which is hidden behind the left rear quaterpanel (in the jack compartment). Your four wheel
drive problem could be as simple as a blown fuse. There are 2 fuses for the four wheel drive system.
One inside under the dash and another higher amp fuse under the hood on the battery side. Or it
could be the more expensive problem like my computer problem or the engagement motor needing
rebuilt. The computer has a diagnostic mode that you can access by pressing the little square white
button on the underside of it with the key turned on but the motor not running. If the little red light
next to the button stays on, then the computer is bad. If the light flashes, the engagement motor is
bad.

the transfer case is sticking from non use, change the lube in the case ( Ford ATF) and drive it for awhile it should be ok then.

I forget what it is called, but it is on front of the transfer case on the drives side, i had to replace one on a suburban

Try to rock it by putting it into D an R it works for my truck.

sounds the wheel senser reading something not working properly