probably a bad u joint

 

Is it a gen 3 or 1 or 2? The live axle models have U-joints that click when they're pooched. The 3rd gen is CV joints. Different, but still a click. Just jack up the front end in neutral one tire at a time and turn the wheel by hand to see if that's it.
Probably just the outer joint.

 

From where you say the sound is occuring it sounds like it may be your gear box, check to see if it may be leaking down onto the idle control arm., if it is a second generation. Also on the second and first generation ram trucks you can easily look at your U-joints with a flash light and even fit your finger in there.

 

Its is the outer U joint, a cheap fix if you do it yourself.