Check the listing for details. Rear Axle Kit Fits GM 12T Diff 30 Spline 5 Lug 31-7/16 Long-ZA K630128. Condition: New. Listed at 78.67 USD. Rear Axle Kit Fits GM 12T Diff 30 Spline 5 Lug 31-7/16" Long SKU: ZA K630128 Brand: USA Standard Gear Condition: NEW MPN: ZA K630128 Manufacturer: USA Standard Gear Manufacturer Warranty: 1 Rear Axle Kit Fits GM 12T 30 Spline 5 Lug 31-7/16" Long, 630128-. USA Standard Gear uses advanced alloys and the latest heat-treating technologies to produce a strong, durable axle. This kit contains all the components to replace, repair, or upgrade axle shafts so your vehicle will be up and running fast.. USA Standard Gear replacement axles are built to meet or exceed OE quality. Engineered for an exact fit, USA Standard Gear axles are easy to install. They are heat treated to enhance strength and provide years of dependable service. This kit contains all the components to replace, repair, or upgrade axle shafts so your vehicle will be up and running fast.