I had the u-joints that "fixed themselves" last winter. They're still not making noise but my truck is getting close to 150k and some posted I would have trouble with them again at some point. So, I'm going to replace the current u-joints with the Moog Super Strength greasable 270. I noticed that Spicer and some other brands that fit my truck had 4 identical snap rings. With the Moogs, one of the rings is c shaped with the ends of the c curved inward. What's the purpose for this?