The clue to a busted CV is lumps of metal and ball bearings fall out when you pull back the boot....my money is on the diff though, I have only ever bust CV's after I welded diffs up, meaning the CV's are normally stronger than the diff. I have not ever had a cv fail on an open diff, and you heard the racket the cv's on the BGL made for a year up the woods, and only then did one break after running with them with a locked front end for another year.
I wouldnt even disturb the cv boots before draining the front diff, and sticking a magnetic pic up tool in the hole and checking for teeth in the bottom, thats if teeth dont come out with the oil.













