2002 ford 4x4 f150 xl 4.6 l cab 1/2 ** 179,000 km on truck ** === turn 4x4 **** to 4 hi or 4 lo indicator lights turn on clicking sound is audioable but truck not going into 4 wheel drive (( any ideas guys ) help would be appreciated

 

Get under the front end and locate the black actuator.
It's vacuum operated and pulls in the locking collar to lock up the axles.
It that happening?
Usually when the light comes on and no 4wd that is the area of the fault because it cannot be monitored in any way but the seat of the pants and lack of front traction.
Check the hoses back to the firewall relays.
Good luck.

 

If it sometimes goes into 4x4 and the actuator is working then you need to replace the shift fork inside the diff. Not that hard!