Our 97 5.4 expedition is not locking in 4x4. The dash lights are switching but 4x4 is not happening. Is there something easy I should be looking for to fix this before I get reamed by Ford service dept?

 

I had this problem in reverse. Would not come out of low 4x4. Check the relay under the hood. Then it may be the motor inside the transfercase. No easy fix there, will have to get inside.

 

I'm also reading it may be a fork or as easy as vacuum line or Vacuum pump. I'll also check the relay. Its switching into Low but just not getting the 4x4. Thanks!

 

Vacuum pump is the most often cause. Just about all of us 97/98 owners have had this issue. Do a search for other threads as this has been covered in great detail several times. I found 12 threads over the last 60 days alone.

Good Luck.