Originally Posted by Steelerssteveo
Mine did the same thing. All I did was find the shifter linkage under the truck and soak it with WD40 and move it back and forth until it freed up.
I had the same thing on my 99 F150. If you live in the salt belt and don't use your 4x4 very often the shift lever on the front differential will corrode up and be very difficult to move and be beyond the ability of the vacuum motor to move it.
What I did was to disconnect the vacuum motor from the lever and move it out of the way. I then put a piece of pipe about 18" long over the end of the lever, and while spraying PB Blaster around the bushing, I started working the lever back and forth. At first it was very tight and it took some time, but eventually enough working and PB that it loosened up to the point that it was smooth as silk.
I think one thing that is important, whenever you think about it, is to actuate the 4x4 while driving. Just flip it on long enough to engage it and flip it off. This will keep it loosened up so that it's available when you need it, especially if you live in the salt belt.