Jack it up with front wheels blocked very well. Put trans in neutral and get up under the rear. Turn the drive shaft with your hands and notice the play. See where the noise is coming from. It should be easy to diagnose where it is coming from.
My guess....ujoints on your driveshaft. SgtDel
aka "Andy"
www.delbridge.net
1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4