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 (TH700-R4) and 4L60-E series transmissions were introduced. Inadequate metering of 2nd gear band servo release oil causes 3-4 clutch failure. The 3-4 clutch and 2nd Gear band are not properly synchronized. 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 failure
• Provides sufficient exhaust so that 3-2 downshifts are smooth
• Calibrates 3-4 clutch feed orifice without creating shift concerns
• Drop-in Zip Valve™ parts install quickly and easily