Sonnax 77898E4K Boost Valve Kit Assembly for GM 4L60E 4L65E 4L70E Transmissions

The Sonnax 77898E4K is a drop-in boost valve kit assembly designed to restore hydraulic integrity and prevent leakage in GM 4L60-E, 4L65-E, and 4L70-E automatic transmissions. This kit addresses a common problem where poor line rise causes 3-4 clutch and 2-4 band failure or poor shift quality due to the EPC solenoid duty cycle causing the boost sleeve to wear quickly.

Key Features:

• Large OE ratio assembly with .470" valve diameter and 1-groove design, specifically for early pump designs with 1.907" length sleeve
• O-ring style design that seals the boost circuit and prevents leakage from the pump body bore
• Hardcoat anodized aluminum construction for enhanced wear resistance
• Compatible with early-style pumps only—transmission will not function properly if the wrong length sleeve is installed
• Drop-in Zip Valve™ design for quick and easy installation

This kit prevents oil from leaking past the boost valve and exhausting at the Reverse orifice, which causes poor line rise. The kit includes the boost valve, sleeve, and O-rings needed for a complete repair. This is the large OE ratio version for early-style pump applications.