tranny or transfer box failure

My X has is making a hard gear change when I accelerate and the let go of the pedal again. Also when driving downhill it does the same when changing gears- therefore I am easy on the pedal. Maybe this is of any help -When I am standing still and put it in drive there is a smal clickingsound from under the car-like it is activating the drivechain or something. My X s 2001 3.0 with 75`miles. When having a oil change the other day- I checked the axles going into the transfer box. Holding on axle still and rotating the other-there was some "give /play" inside the box.
Any clues?