Sonnax Ford 4R100 Transmission Boost Valve Kit Symptoms: Delayed Reverse Low line rise Soft shifts Cause: Severe wear of the boost sleeve due to continuous valve oscillation allows EPC and Reverse boost oil leakage. Correction: Install Sonnax O-ringed valve and sleeve to restore hydraulic integrity. Vehicles with Ford E4OD and 4R100 transmissions frequently have problems with poor line rise and/or soft shifts. These complaints are often caused by severe wear of the pressure regulator boost sleeve, allowing EPC and Reverse boost oil leakage. Sonnax boost valve kit 36424-01K eliminates these problems. O-Rings provide additional protection against leakage at the sleeve bore Sleeve manufactured from highly wear-resistant aluminum alloy Hardcoat anodized aluminum valve combats premature wear