I recently sheared a spider gear tooth off. I went to the 3 main parts stores in my area (napa, oreileys, and autozone, all being very helpful going above and beyond) to try and get a spider gear rebuild kit. According to all their systems my ring gear should be 30 or 33 spines. My yukon has a ring gear with 41 spines. The pinion gear states 11x41 and the numbers 1629 on the other side of the gear head. The larger of the 2 spider gears has 17 teeth and the smaller gears have 10 teeth. The ratio is 3.73. I've attached numerous pictures to help identify this rear differential.

Numbers on the carrier casing.

Ring gear

Pinion

Larger spider gear with sheared tooth

Larger spider gear side view

Smaller spider gear side 1

Smaller spider gear side 2

Ouch. Curious: Any special circumstance that caused this that you are aware of?

. . . and 41 splines on anything this small seems like a lot.This is a 1500, right? Looking around at the interwebs it looks like your choices are 8.5"/8.6" and 9.5" .

The 11:41 means there are 11 teeth on the drive pinion gear and 41 teeth on the ring gear. The splines they refer to are how many splines on the end of the axle shaft that go into the side gears.