The F-trim valve in Allison^®1000/2000/2400 ('00–'05) units is controlled by a PWM solenoid that continuously oscillates the valve. When the valve and sleeve become worn from constant motion the TCC PCS pressure is allowed to cross leak, or escape to exhaust, inhibiting the valve from stroking against the spring and causing converter apply concerns, TCC surge, TCC slippage, code P0741 and overheating. When wear becomes severe it can cause the valve to stick, causing converter release problems as well as apply problems, dependent on where in the bore the valve sticks. Reconditioning the bore and installing Sonnax oversized F-trim valve kit 37000-30K replaces the entire valve train to restore F-trim valve function to normal operation.

• Hardcoat anodized valve combats premature wear
• Annular grooves on the valve help center it in the bore to reduce future side-load wear