So my old 04 F150 XL wont go into 4wd. I have the floor mount shifter to put it in high or low gear, auto trans. Clicks very positive into 4 high, and the dash light comes on to show its engaged. But its not? Goes into 4 low and trucks in 4 low but no action from front axle. Any ideas? Haven't used 4wd since like last March. I don't take the thing off road. Snow was no fun without it.

 

Can't answer your question, but you should be briefly activat 4wd monthly.

 

Sounds like an IWE problem since you have the manual TC lever. (The best way to option a truck BTW.) Do some searching and you'll see literally hundreds of posts on the subject.