Vehicles equipped with 45RFE, 545RFE, 68RFE transmissions can develop erratic or high line pressure due to excessive wear in the OE pressure regulator valve bore. This wear allows critical oil loss, preventing correct line pressure regulation. Without adequate balance oil pressure, the PR valve will be out of its desired position, resulting in line pressure instability and possibly restricting cooler and lube flow. A deteriorated bore can cause lowered line pressure, resulting in soft shifting and burnt clutches. Reconditioning the bore and installing Sonnax oversized pressure regulator valve kit 44912-10K restores pressure regulator action for line pressure control in all ranges.Hardcoat anodized aluminum valve combats premature wearAnnular grooves help center valve in bore to reduce side-load wear