2004 x5 3.0 270,000 miles.

Clicking noise from central area of car when moving in parking lots and other low speed conditions when foot off the a gas pedal. Getting worse everyday it seems. Seems worse if on a slight downward incline. Sometimes a slight shudder in entire car on slope. No symptom when going uphill. I'm suspecting transfer case chain. I had replace rear prop shaft assembly about 10,000 miles back. New flex disc on front shaft. I dont think it's that spline issue. I did the quick fix on actuator rotating the white gear 180. Still have the problem. New CV axles in front and one on back. I get the feeling something is going to freeze up. Seems if it was chain it would be on acceleration and going uphill. Any thoughts?