4 Wheel Drive Stopped working

[triton1]

Can someone help ?
I have a 2000 f-150 4x4 with the electric shift for 4 x4 on the weekend I got in some mud and I had no front wheel pull.
I got under the truck and had my wife turn the selector the light on the dash comes on and the transfer case engages but the (not sure what you call it)
rod on the front pot that runs off a vacuum is not working so I checked all the lines took them off cleaned them lubricated the rod and still no 4x4 it worked great all winter as I use it for plowing now all of a sudden it stopped .Could it be the two little gizmos on the fire wall that not only have the vacuum lines going to them in a cluster but also electrical connections?
I checked all fuses and they are good and no broken wires or leaking lines. HELP

[sau4u]

You should have manual locking hubs on your truck. Lock them in and see if it works. Also check to see if your climate control in your vehicle is also stuck on probably defrost. If that is the case its your vaccuum pump. Easy fix for around $70.00