Like the title states, no sounds while in 2wd but put it in 4x4 and theres a loud clickling/binding from the front drivers side of the truck... Broken axel?

 

could be wheel bearings, could be axle u-joints,

possibly the cad collar not engaged properly, and grinding the collar on the inner shaft. put it up on 4 jack stands, or at least the front axle, and operate the engine to produce vacuum and try to engage the cad.

read and understand this.
http://dodgeram.org/tech/repair/4X4/4x4_engagment.htm