GM Open 8.5 Rear 28 Spline Spider Gears

The GM Open 8.5 Rear 28 Spline Spider Gears represent a critical rebuild component for any mechanic or performance enthusiast restoring or upgrading a GM 10-bolt differential. Spider gears—also called differential pinions—are the rotating elements inside the differential carrier that allow the drive wheels to rotate at different speeds during cornering while distributing engine torque to both rear wheels. Whether you're rebuilding a stock differential after bearing wear, installing a locking differential conversion, or swapping in performance gearing, quality spider gears are essential to restore proper differential function and longevity.

This spider gear kit is engineered for the 8.5-inch GM 10-bolt housing—one of the most common rear differentials found in light-duty Chevrolet, GMC, and S-10 trucks from the 1980s through early 2000s. The 28-spline design ensures proper mesh with the corresponding side gears and pinion shaft, maintaining OEM gear ratios and differential geometry. The kit includes all necessary hardware, the pinion shaft, matched spider gears, and precision washers for correct end-play and clearance. Proper assembly requires careful attention to side gear backlash and pinion shaft preload; inexact installation can cause noise, binding, or premature wear. The complete kit weighs 5 pounds and is designed for bolt-on installation once the differential carrier is removed and thoroughly cleaned.

This component is ideal for DIY enthusiasts and professional shops performing differential servicing, gear swaps, or locking differential installations on second-generation S-series trucks and vans with the open 10-bolt carrier. Proper spider gear replacement restores smooth power delivery, eliminates excessive backlash, and ensures your rear axle assembly operates at manufacturer specification. Installation requires a press, bearing pullers, and differential service knowledge; consult a factory service manual or trusted rebuild guide for torque specifications and assembly procedures to guarantee reliable performance and safety on the road.