There or look at the top of the axle tube for a small nub that has a slightly loose cap on it. Some will have a hose from the axle to the frame with the nub (also known as a breather or vent) at the end of the hose.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!