4x4 switch
 

when i try to put my truck in 4wd it wont ever go. Could it be the solinoid for the 4x4?

ok first off can u hear the hubs trying to lock (truck has to be off but the key in and on)
is so then its either a vacuum line.
secondly manually lock in the hubs then put the truck in 4x4 and drive on something that would make the front tires spin if they dont spin then it could be in the transfer case
other than that i have no clue

More then likely its the vacuum hubs not working. Have you locked the hubs manually and tried it?