Yes, that makes sense. A hardened steel shaft that rides against brass (a soft metal), is rather unlikely to wear. It also seems unlikely the brass bushings would have worn this quickly. I never really checked for the type of play you're experiencing and I don't currently have a 4wd apart right now to compare. The only variable would be the amount of grease you used and the locking hubs themselves. As with a lot of aftermarket parts, the quality/design of your hubs could be a big part of this. Brand new Aisin hubs though??? I bet that will set you back. In the past I've only got used ones and they've always been fine. These are however getting old and finding used things with little to no wear is getting to be more of a challenge. Good luck & keep us posted. Tim