The F-trim valve in Allison^® 1000/2000/2400 transmissions is controlled by a PWM solenoid that continuously oscillates the valve. When the bore becomes worn from constant motion, a loss of converter apply pressure can occur. This can cause converter apply concerns, TCC surge, TCC slippage and overheating. Reconditioning the bore and installing Sonnax oversized F-trim valve kit 37000-33K replaces the entire valve train and restores F-trim valve function to normal operation. Valve is hardcoat anodized to protect against premature wear.