With all the talk about 10 bolts and wanting to beef them up, the 30 spline might not be the way to go.... This was from <a target="_blank" href=http://www.findarticles.com/cf_0/m1185/n3_v31/19071722/p3/article.jhtml?term=>http://www.findarticles.com/cf_0/m1185/n3_v31/19071722/p3/article.jhtml?term=</a> 10-Bolt Corporate The GM 10 Bolt is found in the front and rear. They both use an 8 1/2-inch ring gear. It has a good reputation for having a strong ring and pinion. The 28-spline early models are the most desirable. When GM changed to the 30 spline, they increased the axle diameter without increasing the carrier's bearing, journal size. This weakened the carrier journal, and in extreme conditions, the carrier has been known to break at this point. This occurs before the smaller diameter 28spline axle would have broke. Gear ratio split is 2.56:1 I assume this is true I know some folks (like ChevyCaGal/Steph) has been looking for 30 spline units for strength, but that MAY not be the way to go. As stated before I had good luck with my well maintained/and abused 28 spline unit. There is a Right way, a Wrong way, and then there is My way. The latter is usually the most fun!