Fits Sierra 1500 Base Model; 30 TEETH; 7,200 lb Hydraulic Power Brakes, 8.50/8.625 Ring Gear Saginaw - American Axle; 10 Bolt Differentialor Sierra 1500 Base Model; 30 TEETH; 7,200 lb Vacuum Power Brakes, 8.50/8.625 Ring Gear Saginaw - American Axle; 10 Bolt Differential