Ford AOD (FIOD) A+ Superior Overdrive Super Servo This Super Servo Superior will improve all Ford AOD Transmissions. This Problem Solver deals with these problems: Premature overdrive band failure, having to search through old cores for old covers, a lack of holding power and a less than positive 4th gear shift. Superior's AOD Super Servo is perfect for heavy duty and high performance applications. This product is American Made! Built from 6061-t6 billet aluminum, provides 11% more apply area than the stock "A" servo and is designed to increase holding capacity and boost performance!