THE NEW CHRYSLER ULTRADRIVE four-speed transaxle is the first production transmission to employ fully-adaptive electronic controls. Adaptive controls are those which perform their functions based on real-time feedback sensor information, just as is done by electronic anti-skid brake controls. Although the transmission is conventional in that it uses hydraulically-applied clutches to shift a planetary geartrain, its use of electronic logic to replace the function of many mechanical and hydraulic components is unique.
This paper describes the adaptive controls, how they function in upshifts and downshifts, the simplicity they permit in the clutch and geartrain arrangement, their effect on the design of certain components, and the advantages they offer in diagnostics. It also describes the hydraulics and how certain unique challenges are met in the Ultradrive transmission.