I have a 2001 f150 with the switched 4x4. when i get in and turn the key you can hear a clicking in the dash for a fiew seconds. when you switch it to 4x4 it doenot click or ingage the 4x4 and only if the clicking is going on in the dash and you flip the switch will the 4x4 light come on but still no 4x4. anyone have any advice?
2 vacuum lines run off the diff. and go to two actuators or relays that should be located behind the battery on passenger firewall. you can test it by putting a vacuum gauge on it an see if it pulls a vacuum and start from there. just check the line for holes or anything that might have burnt through it. usually the cluck is the transfer case locking into 4wd not the front diff. inside the t-case are shift forks that lock in the gears thats what clunks
