Does anyone know what could be wrong with my truck?
When you put it into 4 high or 4 low the dash indicator lights up but nothing happens - no 4wd
It is a shifter on the floor

Also - had cracks on the door too
I got new doors before warranty up ford customer service very
nice - had cracks on new doors 18 months later - out of warranty would not fix - I was not very happy - Hard to have Ford pride with chevy driver friends when doors cracked and 4 WD won't work - they had to pull me out!!! YIEE

 

The front differential is engaged by a vacuum motor on the axle housing. You might want to check there.

 

Just had the same problem with 97 f150. Vac motor ok but electric vacuum switch on firewall on passenger side(2 of them)was sticking. removed ,tapped on bench and loosened valve inside, added small amount of fine oil, re-install and works fine.May also want to check vac lines from switches to vac motor. Vacmotor will come apart carefully.consists of front and back cover and rubber diaphram . Mine had fine dust which had hardened like concrete. Hope this helps

 

Thanks for the input

I brought it in - plunger assembly at front diff was stuck
freed up and lubed - $55

I was very happy

 

Thank you for telling us the solution . That was very consider-it.