Superior Ford AOD A+ Automatic Transmission Billet Overdrive Super Servo Kit Lincoln Mercury. This Problem Solver deals with these problems: Premature overdrive band failure; Searching through old cores for old covers; Lack of holding power; Less than positive 4th gear shift. The Superior Super Servo helps to eliminate premature overdrive band failure. This AOD "A-Plus" Super Servo delivers better holding capacity. Positive 4th gear shift. Superior's AOD Super Servo is perfect for heavy duty and high performance applications. American Made, built from 6061-t6 billet aluminum. 11% more apply area than the stock "A" servo designed to increase holding capacity and boost performance.