There are three different side-gear tooth counts: 16, 17, and 18. Tom says the 17-tooth (left) is the strongest. The 17-tooth side gears require specific pinion gears. Tom sells new 17-tooth 30- and 33-spline side gears. The spline count must match your axles. A 33-spline side gear can be used in a 30-spline by boring the case.