Since I had the axles out to replace the knuckles, it was a good time to take a look at them. Although I'd never had a failure of the stock Spicer shafts (which were new several years ago when I built the axle), I was about ready to. Note the twist starting to form in the splines of the righthand inner axle. These were cut splines since this was a custom-length axle. Since the Spicer axles are mild steel and the hardening doesn't run too deep, this spline twisting is what happens after a while.