clicking when turning

I have a 1985 190E w/216,000 miles on it. We have started to hear a clicking from the rear end when going around a sharp corner to the right. Very seldom hear it when turning left. Gets louder if you accelerate when going around the corner, like at an intersection. The boots at the rear look fine, no holes or cracks. When I jack up the rear end and turn the wheels by hand or turn the drive shaft, I hear a metalic clicking coming from the rear end, or flex joint at the front of the rear diferential, as I quickly turn the wheels first forward and then backwards. When it changes direction, it clicks. Could it be the flex joint, or is the rear end low on fluid? Or are my CV joints going out on that side?