Ford AODE 4R70W 4R75W Transmission Main Pressure Regulator Valve Symptoms: Erratic buzz Low line rise Low Reverse boost Poor shift quality Premature band failure Premature clutch failure Soft shifts Uncontrolled pressure in Reverse Cause: A worn main regulator valve and worn reverse boost sleeve. Correction: These direct replacement main regulator valves prevent EPC oil from leaking to exhaust, while the replacement pressure regulator boost valve and sleeve kit restores the level of line rise required for reverse. '96-later A common complaint in vehicles with AODE/4R7OW transmissions is low line pressure or throttle sensitive buzz, especially when hot. This is often caused by a worn main regulator valve. The valve frequently wears on the boost spool diameter and allows EPC (electronic pressure control) oil to leak to exhaust. This leakage results in poor line rise. When the oil temperature increases, the oil becomes less viscous and more leakage occurs. The two Sonnax replacement assemblies 76948-01 and 76948-09 eliminate the above problems with a direct replacement main regulator valve. Another common complaint with these transmissions is poor reverse boost, often the result of a worn pressure regulator boost sleeve. The sleeve should be checked while replacing the main pressure regulator valve. Sonnax offers a replacement pressure regulator boost valve and sleeve kit 76948-02K. These closely toleranced parts are made from high-quality aluminum and have been specially hard-coated to eliminate excessive wear. Annular grooves have been added to the pressure regulator valve to allow an oil film to surround the valve, thus centering it in the bore to prevent side loading which causes premature wear. NOTE: '91-'95 PR valve and '96-later PR valve designs are not interchangeable