I Need help with rear end knocking noise

[jcloud6]

I searched the post but could not find any help with my truck rear end problem. The rear end started this loud thumping/knocking type noise. I put on jack stands, started the engine and put it in drive. With the rear wheel spinning I was able to pin point the location of the noise. Its the 1981 C10 orginal factory non-posi rear end. The oil level is good, however I did notice the rear pinon yoke had a small wobble while the rear wheels spinning. Is it possible the front and rear pinon bearing is worned out and the wobble is causing the noise?

Any assistance will be helpful

Thanks