200-4R / 4L60 TV Boost Valve Kit

The Sonnax 77917-03K is a direct-fit TV boost valve kit specifically designed for GM 200-4R and 4L60 automatic transmissions. This kit addresses common internal transmission issues like soft or delayed shifts, premature 3-4 clutch failure, and reduced band life, which are often caused by throttle boost (TV) valve oil leakage and insufficient line pressure rise. Constructed from hardened steel for superior durability and wear resistance, the 77917-03K features a .471" bore diameter and a factory-style sleeve. Its primary function is to prevent oil loss that occurs between the outer diameter of the TV sleeve and the transmission's pump body, thereby ensuring proper hydraulic pressure and improving overall transmission performance. Sonnax offers this TV boost valve kit in three different sizes: the 77917-02K with a .423" diameter for V6 applications and smaller vehicles requiring minimum line pressure, the 77917-03K with a .471" diameter, and the 77917-04K with a .500" diameter for applications demanding maximum line pressure and a firmer shift feel, particularly in high-performance scenarios. The 77917-03K is explicitly recommended for V8 applications and situations where higher line pressure is needed, such as for towing and off-road driving.