3.21 ratio. 4WD. Gear assy. PartQualifier: heavy duty 3.21 ratio. PartQualifier: heavy duty 3.73 ratio. Rear. Differential Pinion Gear. Exc.Limited Slip Differential. Gear used inside the Differential case that is splined to the axle shafts and meshes with the Differential Pinion Gears. Side. Center. Drive.