You might have been leaking for a while and are now at low fluid level. This could lead to a total failure.
I faced a situation where (while still under Starmark warr., thank goodness) my diff began to make a lot of noise.

Checking the PO's repair tickets I see where a front seal was installed at abt. 50K. I suspect it was run low...
and was repaired to stop the leaking front seal, but at 97K I experienced the failure.

Whatever you do keep the level correct if you continue to drive it.

Luck to you,
DanielW