05 pathfinder clicking noise

[contactmo]

So over the past month I have begun to hear a clicking noise coming from the front half of the truck. Here are some scenarios of what will create the rhythmatic clicking noise.
Does not occur in park
It happens at low speeds (<20 mph) while in drive.
If I bump it into neutral while coasting the noise will go away.
If I put it in 4H I never hear the noise.
The clicking advances its rythm with engine RPM not speed while driving.

Any ideas?