I wonder if this is related to your "transfercase" problem you were having...
either way I would love to give an guess but over thei interwebz its difficult to iron down where noises are coming from
, typically grinding isnt good... duh right?
Not to hurt your feelings or scare you but personally I love isolating a major noise like a diff noise and doing my tear down and locating the problem, some minor noises can be narrowed down with a stethoscope or chassis ears and combine with the those readings and considering symptoms and what could cause the noises you repair the part you have deturmined to be the failure... during the repair process you dont really find the smoking gun, put it back together and viola, it did repair the problem... I am guessing this wont be a problem in your situation, there will likely be a smoking gun