Boost Valve Kit for GM 6L45/6L50/6L80/6L90 Transmissions

The Sonnax boost valve kit (104520-12K) is engineered to resolve common performance issues found in GM 6L45, 6L50, 6L80, and 6L90 transmissions. Vehicles equipped with these transmissions may suffer from insufficient line rise in drive ranges, leading to soft shifts and potentially burnt clutches. These symptoms often stem from the continuous oscillation of the boost valve within its sleeve, causing excessive wear and allowing critical EPC fluid pressure to leak to exhaust. This kit utilizes upgraded materials and precise, minimal clearances to combat wear and restore optimal hydraulic control. Additionally, the sleeve incorporates a larger EPC feed orifice, which contributes to quicker throttle response. A new, stronger pressure regulator valve outer spring is provided to replace weakened original springs, delivering a modest 5 psi increase across the pressure curve for improved performance. The Sonnax boost valve kit is designed as a "Zip Valve" part, meaning it installs quickly and easily as a drop-in replacement. The kit contains the necessary valve, sleeve, and spring to complete the repair. By addressing the root cause of EPC fluid leakage and wear, this kit helps to prevent further transmission damage and restore proper shifting characteristics.