Sounds like it could be the transfer case chain. Doing the transfer case chain on mine right now. the change slacks over time then slips over the sprockets. Not necessarily going to see any flakes as the chain is stretched not fragmented. If caught early enough the sprockets don't need replaced. There are some vids on youtube demonstrating the sound. See if it's the same.



CV's typically sound more like clicking and in all the car's I've had, if the boots don't tear I've not had them fail.