Clicking Noise: CV/Half Axle, transmission-center differential, tie rods?

1999 Subaru Outback: The vehicle has been making a clicking noise whenever I turn the vehicle left or right turning slowly. It is most notable when I drive slowly around the parking looking for a space making left, right turns or backing into a parking space. I have also noted that this clicking noise is more prominent after I have driven over one hour's time or more. This noise does not exist when I drive straight down the road, or if I drive 15 minutes to the store and make turns. I can feel the clicking after driving for one hour or more and reminds me of turning a 4WD vehicle when it is engaged in 4WD.

The vehicle has gone to the shop and I have received three different diagnosis:

1). Need to replace the half-shaft/CV joints 2). Need to replace the transmission. The center differential is shot. A common problem with AWD vehicles 3). Replace the tie-rods/check the boots.

One final note: All of the CV boots and tie-rod boots are in good shape. There is no wear and tear what so ever.

Totally stumped