Sonnax 4L60E Transmission Boost Valve Kit 77898E-3K A common problem in GM 4L60 transmissions is burnt bands and/or 3-4 clutches. This failure can be reduced by eliminating throttle boost oil leakage. Sonnax TV boost valve kit 77917-500 will eliminate these problems for a variety of applications, and will boost pressure higher than TV boost valve kit 77917-471 due to the increased .500" valve spool ratio. Returns higher pressure than OE-ratio valve Boost valve and sleeve are made from hardened steel for better wear resistance O-rings on sleeve separate throttle pressure and reverse boost circuits, providing additional protection against cross leaks O-rings prevent loss of oil between the outside diameter of the throttle valve sleeve and pump body Contents Valve Sleeve O-Rings (2)