The 4wd on my 2000 f150 XLT ext cab 5.4l is not working light comes on the dash like everything is normal but no front wheel engagment swith to 4wd low and you can hear the transfer case kick in but still nothing at the front wheel. any advice??

 

Inspect everything under it would be the first thing I would do

 

I think they have some vaccum lines under the truck that are notorious for coming loose

 

An idea where these vacum lines are???

 

Front axle housing

 

Take the vacume actuated shift fork off the front diff and lube it with wd-40 and move it back and forth till it moves freely! Then reinstall. If that doesn't work trace the vacume lines from there to the passenger side fire wall looking for leaks.