Differential Re-Gear Kit for GM 8.5" with 4.11 Ratio and

The Zumbrota Drivetrain YGK2339 is a comprehensive re-gear and limited-slip differential kit designed for GM 8.5” axle applications. This kit provides a significant upgrade for vehicles seeking improved performance and traction. Complementing the re-gear components is the Yukon Dura Grip positraction limited-slip differential (LSD). This LSD unit features 28 splines and is engineered to distribute torque effectively to both rear wheels, improving traction during acceleration and cornering, especially in slippery conditions. The kit is specified for GM 8.5” differentials, featuring a 30-spline pinion gear and a 10-bolt ring gear pattern. It also includes 2.25" OD bearings and all the necessary installation hardware to ensure a complete and proper setup. The fitment explicitly covers 1970-1981 Firebird Trans Am models and 1970-1977 GTO models, along with 25 other specific vehicles, or any custom build utilizing a GM 8.5” differential. This re-gear kit is a substantial upgrade for muscle cars and performance-oriented builds, offering a balance of improved off-the-line performance with the enhanced traction benefits of a limited-slip differential.