Motive Gear G875373 7.5" Rear Ring and Pinion for GM (3.73 Ratio) 8620 Steel Performance Differential Ring And Pinion Ratio: 3.73 Pinion Spline: 27 Ring Diameter: 7.5 Pinion Diameter: 1.438 Ring Gear Teeth: 41 Pinion Teeth: 11 Position: Rear