In the Passanger Cars... The GM 12-bolt debuted in 1965 and was mass-produced until 1972. It features an 8.875-inch ring-gear carrier held in place with two internal main caps. The pinion gearshaft measures 1.625 inches in diameter and is shimmed to achieve the proper pinion depth. The pinion gear splines to a yoke that mates with the driveshaft's rear universal joint. The three most common types of yokes are the 1310-, 1330-, and 1350-series units, but the 12-bolt generally uses the smallest, 1310-style U-joint. Factory axles come in a 30-spline configuration and slide into the side gears. Instead of bolting the axles in place, stock GM >> 10- and 12-bolts use small C-clips over the ends of the axles to hold them in place. This requires removing the rear cover, draining the oil, and extracting the center pin in order to pull the C-clips to remove the axles (whew!). Axle bearings are pressed into the tube with the outside diameter of the axleshaft acting as the inner bearing brace. The downside to this idea is that if the bearing fails, it takes out the axle too.