Hi all!
I am new to this site, and was looking for anyones suggestions on what might be my problem before I take it in somewhere. I am a female, and I own a 2001 F-150 4x4. I live in Iowa/Nebraska, and we dont get that much snow but when we do, the 4x4 HIGH works great. The problem is, when I turn the switch back to the "off" position, it doesnt always seem like it turns off. The light on the dash panel goes away, but you can tell it is still engaged. Sometimes it works fine, but not always. I know its bad to drive at high speeds in 4 wheel drive and especially on dry surfaces, so I get nervous when this happens. Does anyone know what may be the problem, and is it an expensive one to have fixed.
Thanks all for your help.

 

If it works to engage, that eliminates some of the possible problems, including bad shift fork. As it sometimes disengages, the disengage solenoid should be okay. I would look for any cracks in the vacuum line between the disengage solenoid and the front diff. I believe the disengage solenoid is the inboard one, although I could be wrong. Wouldn't hurt to check both.
Also how fast are you going when you switch to 2wd. I don't believe there is a speed limiter that would keep it from disengaging until below a certain speed, but Ford in the OM recommends not switching in and out of 4hi above 55.