Is the 4x4 system a floor shift or electronic shift transfer case. Many 4x4 noises on the floor shift transfer case will cause more noise due to limited insulation added to the cab and noise transmitted through the shifter rod into the cab. And you also have to consider these trucks are built with a better a chassis and it doesn't take much to transfer noises, unlike the older trucks. When does the noise happen most often?
Here is one bulletin that may apply.
Some customers may comment on various noises associated with 4wd operation
One of the many advantages of the new 2015 MY pick-ups is the cabin is quieter compared to previous model years. For that reason, when the vehicle is in 4WD mode (HI or Low), there may be some noticeable sound from the transfer case. This sound may be described as a whining. This sound can be described as being a very broad band frequency.
With the vehicle in 4WD mode, this sound will be present on both acceleration (30-40 mph) and deceleration. The sound will increase when driving on dry pavement in 4WD. It can also be identified since it disappears or reduces considerably in 2WD mode.
Before beginning any diagnosis it is imperative to review the Symptoms - Transfer Case in SI and perform the necessary inspections. In all cases the complaint vehicle should be compared to another like vehicle before beginning any repairs.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.