Front or rear? In either case, there's no "check" required. If there's no gear oil seen dripping out of the front axle at the inner C and you don't see any suspicious patterns of fluid being "flung" out of the rear drums (and it smells like gear oil vs. brake fluid), you are okay. Otherwise you will need to replace at some point.
If you really want to test it, park on a sidehill for a while so that any leaking lube would tend to move towards the axle ends via gravity. Next time park facing the other way to test seals on the other side Most times you can see leaks without that.
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