Heavy-duty vehicles with Ford C6 transmissions often display poor line rise, which results in erratic shift timing, Reverse shudder or direct clutch failure. This can be caused by excess wear at the inside diameter of the boost sleeve. This wear allows oil to leak past the boost valve to exhaust, resulting in poor or no line rise. The outside diameter of the boost sleeve may allow leakage through the valve body, which results in insufficient line rise. Recover the hydraulic integrity of the boost circuit and restore proper line rise by installing Sonnax diesel-ratio boost valve kit 36946-02K. Diesel-ratio kit restores OE boost pressure O-Rings provide positive seal Sleeve manufactured from highly wear-resistant aluminum Hardcoat anodized aluminum valve combats premature wear Note A number of boost valve kits are available for this unit: Normal line pressure boost (gas ratio): Kits 36946-01K, 36946-04K and 36941-01K. Increased line pressure boost (diesel ratio): Kits 36946-02K and 36946-03K are recommended for all heavy-duty applications. Kit 36941-01K works in early model "clicker" versions with screw-on boost valve end plate. Kits 36946-01K, 36946-02K and 36941-01K include O-rings to provide additional protection against both cross leakage and oil exhausting through the valve body bore. Contents Valve Sleeve O-Rings (4)