77898E-K - Sonnax 4L60E 4L65E 4L70E Transmission Boost Valve Assembly Kit .490

4L60E 4L65E 4L70E Transmission Boost Valve Assemebly Early pump design, .490" Dia., O-ring style • Diameter: 0.490" Vehicles with a 4L60-E, 4L65-E or 4L70-E transmission 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 offers four versions of reverse boost valve and sleeve kits for early pumps. There are two O-ringed versions, 77898E-K for oversized ratio and 77898E-4K for OE ratio, and two factory style versions, 77898E-3K for oversized ratio early pumps and 77898E-6K for OE ratio.