2002 GMC C1500 rattling noise coming from driveshaft/rear o

I have a 2002 gmc 4x4 club cab. has 456 rear end. I just had the steering damper and arm replaced, and front end alignment. several days later I started hearing a slight rattling,but only on deceleration, not when i accellerate, sounds alittle louder now after several more days of driving on it. I can hear it best at around 10-20mph. The u-joints look solid. the rear pinion shaft has very little play up and down, but I believe it to be normal. really loud when I jacked up the rear onto stands, started, put into drive, gave some gas(no noise) let off the gas(noisy). I suspect the bearings are going out. any info would be helpful. Thanx