The truck is also the manual 4x4 shifter on the floor.
It all started out 2 months ago when in 4 it was humming louder than normal at high speeds and pulling to the left when in 4x4. Than it went to not wanting to go into 4x4 for awhile but the light was on but wouldnt lock in. And it would take awhile to get out of 4x4 and when it did it would CLUNK loud. Now today it would lock into 4x4 at all. What are the problems guys??? thanks alot

 

check the vacum actuator system. Its on the firewall next to the starter relay. Behind the battery. Look for vacuum leaks. Might need to test it. Check the transmission fourm for the instructions on how to do that. Maybe its in the drive line section to.