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Country/Region of Manufacture: United States

Manufacturer Part Number: 77898E-6K

OE Spec or Performance/Custom: Performance/Custom

Brand: Sonnax

Manufacturer Warranty: Unspecified Length

4L60-E, 4L65-E

Boost Valve Kit
Part No. 77898E-K

Early pump design, .490" dia., O-ring style with increased ratio

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-K is an increased ratio assembly that will restore hydraulic integrity and prevent leakage in units with early-design pumps.

See graphic in photo gallery of the chart for usage details and other boost valve options.

  • Sleeve
  • O-Rings (2)
  • Valve .490", No Groove

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