Common problems in vehicles with GM 4L80-E and 4L85-E transmissions are uncontrollable line rise (upward of 500-600 psi), high line pressure in Reverse, buzzing noise, broken direct clutch drums and/or broken cases. These problems are usually caused by Reverse boost oil that enters the torque signal circuit due to a wear-created cross leak at the sleeve. High line pressure and buzz is created by oil leakage past the aluminum balance plug. Sonnax boost vavle kit 34200-03K eliminates these problems.

• Hardened steel boost valve with over 20% wider spools to provide better durability and increased sealing contact area
• Boost valve spools have annular grooves to reduce side-loading that causes wear
• Valve and sleeve are manufactured to close tolerances to restore proper clearance and hydraulic integrity
• Kit includes a replacement aluminum balance oil plug with an O-ring to ensure proper sealing and adequate back pressure on the pressure regulator valve
• Drop-in Zip Valve^™ parts install quickly and easily