8.6" GM 4.88 Rear Ring & Pinion, Install Kit, Axle Bearing & Seal. USA Standard 8.6" GM, 4.88 Ratio Rear Ring & Pinion Gear Set and Master Install Kit Package, with Axle Bearing & Seals. USA Standard Gear Ring Gear & Installation Kits are an easy way to re-gear a differential with one simple part number. The kits package a ring and pinion set with a Master Installation Kit that contains all the bearings, seals, and small parts needed for a proper install. USA Standard Gear employs rigorous in-house quality testing and inspections to ensure its gears pass dimensional, material, and fitment testing.