On the XP version that has the popping issue. When you are turning the axle, the ball is in the race of the inner race (star) and the outer race (cup or housing) and the balls are constantly moving and being pushed, like a greased grape being squeezed between your fingers, and would have a tendency to shoot out. The cage is there to hold the balls in place. Normally the windows in the cage are only about .001-.004" larger than the diameter of the ball, so they hold them in place very effectively.
For a couple months in 2008 the company that makes the axles for Polaris screwed up and made the windows a bit too large, so when the ball gets squeezed between the inner and outer race and shoots out, it hits the side of the race, causing a clicking sound at about 6 times per tire revolution (or close to that)
It should not cause any durability or strength problems, merely an annoyance factor. If it did cause a durability issue Polaris would have done a recall, but since it's not they didn't.
I received this information from Big_T from another site.
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