Clicking/clunking nosie from differential area

Last week after many days of cold, we had a warm day--60 degrees.  Stalker #8 had not been out for a couple months, so I took advantage of the warm day to go for a drive.  Immediately upon leaving the driveway, I noticed was a loud click almost a clunk from the differential area. It was the kind of noise that definitely indicated something mechanical was not functioning correctly. I slowly drove around the neighborhood trying to figure out what was causing the noise.  At the time, my best guess is the click/clunk occurred about every driveshaft revolution, but it was maybe less frequent than that.  The noise did not occur in reverse.  Back in the garage, I jacked up the left wheel and spun it by hand--no noise.  I started the engine and spun the wheel and still had no noise.  Did the same thing with the right wheel with the same results.  I took it back out on the road and the noise was gone.  I drove it about 10-12 miles with no noise.  It's been too cold to drive it again--single digits today.  I have a Torsen diff.  Any ideas will be appreciated?