And I don't have anything to technically tell me what there supposed to be called. I know i've heard the smaller ones referred to as the pinion gears before. But I've always referred to the side gears as spiders even when I was only talking about the sides. I'm more inclined to believe that on an open rear the side gears break first. Mostly because I believe the pinion gears actually share/split the load but generally only one side gears sees the entire load. I've never stripped the splines, always shattered the side gears or a combo of side and pinion gears. Again that is just my experience.