ALUMINUM CENTER SECTION Ring Gear Diameter: 8.50" Ring Gear Bolts: (10) 3/8" x 24 RH Thread Cover Bolts: 10 Carrier Breaks: 3.73/3.92 Superior Ring and Pinion sets are manufactured from premium 8620 steel. Computer controlled machining is performed by both Gleason and Phoenix gear cutting machines. Precise heat treating, honing and lapping is performed to provide ideal contact patterns for smoother, quieter and cooler operation as well as easier set up.