You'll have to follow the lever. I would take your boot off(rubber thing by lever) and remove your lever and then spray everything that is involved with it working. Make sure it's warm or it won't do much penetrating for you.
Let soak for hour then spray the heck outta them again. It worked for my auto tranny that stopped working I assume it should work in this situation.
Got plugs and wires to do on my 97 f-150 so if I get a chance I'll try to look at the system(need to bend 4wd lever anyway) gotta love 3 inch body lifts