77898E-4K - 4L60E 4L65E 4L70E Transmission Boost Valve Assembly Kit .470 Sonnax 77898E-04K

4L60E 4L65E 4L70E Boost Valve Kit Part No. 77898E-4K Valve .470", 1 Groove Sleeve O-Rings (2) Replaces early pump design, 1.907” length (long) sleeve, large OE ratio assemblies. GM 4L60-E and 4L65-E transmissions frequently have poor line rise, which can result in 3-4 clutch, 2-4 band failure or poor shift quality. The duty cycle of the EPC solenoid causes the boost sleeve to wear quickly. Oil entering the torque signal orifice leaks past the boost valve and exhausts at the reverse orifice, resulting in poor line rise. Reverse oil can exhaust both to the sump and back through the torque signal orifice. The outside diameter of the boost sleeve also allows some leakage through the pump body, which decreases pressure rise. Sonnax boost valve kit 77898E-4K is a large OE ratio assembly that will restore hydraulic integrity and prevent leakage in units with early-design pumps. See chart below for usage details and other boost valve options.