Sierra 2500HD AT4X 2024-2025 Chevy Super Stock Kit (Upper Control Arms, Idler Arm Support & Shock Extenders) by Cognito

The Cognito110-P1268 Super Stock Kit is designed specifically for the Sierra 2500HD AT4X models. Since these trucks already come factory “leveled” via torsion bar and key clocking, a traditional leveling kit is not an option. Instead, Cognito engineered this package to improve ride quality, steering longevity, and suspension performance — without altering factory ride height.

From the factory, these models sit at approximately the same front height as a 3” leveled truck, but GM added a 1.5” rear lift block — resulting in a noticeable nose-down stance. More importantly, the increased ride height creates tie-rod angles that are no longer parallel to the centerlink, which can accelerate wear on the pitman and idler arms.

This kit includes Cognito’s patented Pitman and Idler Arm Support Kit (PISK), engineered to properly support and control steering system movement. By correcting this inherent GM steering flaw, the kit helps prevent premature pitman arm, idler arm, and front tire wear — addressing the root cause rather than masking it with a steering stabilizer.

Ride quality is further enhanced by addressing the limited factory droop travel. In stock form, these trucks have only about 2 inches of front droop travel, leading to a harsh top-out feel over dips and uneven terrain. Cognito developed precision DSSV shock extenders that increase droop travel to just over 3 inches — a 50% improvement — delivering noticeably better compliance while maintaining factory geometry.

To round out the package, Cognito includes its SM Series Upper Control Arms, purpose-built for AT4X and ZR2 models. While not required for ride-height correction, these boxed sheet-metal arms add durability, increased caster, and long-term reliability — all while giving the truck a more aggressive, performance-oriented appearance.

Features & Benefits

• Designed specifically for GMC Sierra 2500HD AT4X models
• Improves ride quality without altering factory ride height
• Increases front droop travel from ~2" to just over 3"
• Patented Pitman & Idler Arm Support Kit prevents premature steering wear
• SM Series Upper Control Arms with added caster
• Maintenance-free pivot bushings and ball joints
• Powder-coated semi-gloss black finish
• DSSV front shock extenders included
• Engineered and assembled in the USA