The backlash is set w/ side rings, so you can quickly and easily adjust it, aka, no shims involved. Very easy backlash setup.
DR, I'm a little confused about the spider gears... When I took out my open carrier a long time ago, to put in an ARB, there were 4 spider gears in there. I'd assume that would be a 4 spider... But I know for a fact I have 33 spline rear axles. My truck is a 2002 model. Could it be that they changed from a 31 spline to a 33 spline, but kept the carrier the same until a later year? Man, I wish I hadn't sold that open carrier. Would have been awfully nice to confirm my memories on the thing. But I'm damn near positive it had 4 gears in there.