Any clicking or ratcheting noise from the front wheels) is a sign the automatic hubs are not locking.. An Easy test is to get under your truck and rotate the front axle shafts (not the drive shaft).. Rotating the axle shafts by hand mimics 4x4 being engaged. After a few revolutions an Autohub should lock in and be impossible to turn.. If you are able to keep turning the axle it indicates the hub is bad/gunked up. For manual hubs the test would be to get under the truck with the HUB unlocked (4x4 off) and verify the axle shaft rotates freely. Next lock the hub, the axle shaft should be impossible to turn. If you are able to turn the axle it indicates the hub is bad/gunked up.
Worn or heavily greased autohubs tend to buzz or chatter when going around corners (the hub mechanism is partially trying to engage). If you lock the hubs and the noise goes away then a good hub cleaning is in order.