Common problems in vehicles with a 4L80E transmission include uncontrollable line rise (upward of 500 psi), high line pressure in reverse, broken direct clutch drums and/or broken cases. These problems can be caused by excessive EPC torque signal pressure. The Sonnax self-regulating reverse boost valve 34200-10K eliminates these problems by limiting EPC pressure.

• Hardened steel boost valve has an encapsulated relief valve that will allow EPC pressure to exhaust if it exceeds 95-105 psi.
• 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.
• Closely toleranced sleeve restores the hydraulic integrity between the valve and sleeve.
• O-rings have been added to the sleeve to provide a positive seal that compensates for pump bore wear.