Why is there whining in your my transfer case when in 4x4?

the whining comes from the gears in the transfercase. The gears are larger and smaller dependin on what range your in and the noise is typical notice the rpm to whine ratio, however if the noise is extremely noticeable you may want to check the gear oil in the tcase it may be low. The more the gears become worn the louder the whine will become. Just as a manual trans. is the same.