4L60 4L65 4L70E Sonnax Servo Release Check Valve Kit Part No. 77701-076 2nd Gear Servo Release Technicians would like to find a way to successfully extend the life of 3-4 clutches and improve the 2-3 shift feel. They have been trying, with limited success, since the GM 4L60 (700-R4) and 4L60-E series transmissions were introduced. Inadequate metering of the 2nd-gear band servo release oil causes 3-4 clutch failures. The 3-4 clutch and the 2nd gear band are not properly synchronised. Sonnax servo release check valve kit 77701-076 is a unique solution that combines an orifice with a ball check valve to resolve these problems. Improved design meters servo release oil, reducing 3-4 clutch failures Provides sufficient exhaust so that 3-2 downshifts are smooth Calibrates 3-4 clutch feed orifice without creating shift concerns