How do you know it is a traction differential in the first place?
There are only two differentials you can positively identify without pulling the case. Jack up the rear of the car to get the rear wheels off the ground. Turn one rear tire. An open differential in proper working order (not welded or shimmed spiders) will either rotate the opposite tire in the opposite direction or the opposite tire will remain still. With a Detroit Locker, you turn the one tire forward (the other tire will also be rotating in the same direction), then immediately reverse the tire you're turning and you should hear the clutch ratcheting as it unlocks.
If both rear tires turn in the same direction then there is some kind of traction differential but you'd have to pull it to see what guts it contains. It could be gear, or one of the clutch pack units.
Not to give you a snoot full, but "posi", an abbreviation for Posi Traction, is GM's marketing name for its traction differential.