2000 GMC Sonoma Grinding and popping noise

I had a truck come to my shop about a month ago with a complaint of a grinding and popping noise coming from the rear end. I checked the U-Joints, the one at the pinion flange end has a very tiny amount of play in it, but the rest are tight as can be. Now the drive shaft center bearing is completely shot. When you accelerate and put a load on the drive-train, you can hear and feel a grinding accompanied by a clicking sound. Coasting and in neutral, nothing. Up on stands, under acceleration you can hear the grinding, especially after letting off of the gas. It mostly resonates througn the left axle. I pulled the diff apart and found a lot of metal shavings, and some damage to the ring gear. I replaced the ring and pinion, the diff bearings, and the axle bearings and seals. Unfortunately, that did not fix the problem. Same symptoms. Any suggestions?