What year is that?
It looks like it has standard hubs on front. If its 2005 or later, watch out. Warn has come up with their latest version of "automatic" hubs and sold them to Ford in time for the 2005 version.
I just pulled out a friend with a 2005 F250 with auto hubs. Turns out that they are not all that reliable.
However, Warn did make them so that they have a manual option. But, if you don't use it from time to time, the knob freezes up and breaks when you force it.
My friend's left front did not engage and the knob was frozen. Fortunately he did not force it, so we will pull the hub and free the knob later.
This latest attempt uses vacuum to engage the hubs. There is a vacuum pulse solenoid, a fairly fragile vacuum line going into the back side of the spindle, plus a couple of seals that can go bad and stop it from engaging.
One of the seals, naturally the one to go bad the most often, requires you to remove the entire spindle to replace it.
Your truck looks like it has the old style hubs though.