890528 The Chrysler A-604 Ultradrive 4-Speed Automatic Transaxle Berthold Martin and Thomas Nogle Chrysler Motors Corp. ABSTRACT A new kind of four-speed * automatic transaxle, engineered from concept specifically for real-time closed-loop electronic control, has been designed, developed, and put into production by Chrysler Motors Corporation. This overdrive transaxle combines two simple planetary gear sets with five disc-clutches, five hydraulic spool valves, and four direct-acting three-way solenoid valves to achieve all operating modes. It uses no bands and only the torque converter stator has a freewheel element. It provides both a fourth ratio and increased engine torque capacity in the same package space used by the previous three- speed transaxle. At the same time, fewer parts are required and manufacturing is more readily automated. MAJOR DEPARTURES FROM PREVIOUS practice became necessary in several key areas to meet the following requirements in design and development of the A-604 Ultradrive four-speed transaxle: Input torque capacity at 542 N*m. A ratio spread in forward gears of at least 4.0 for performance and fuel economy. Superior shift quality. Vehicle packaging interchangeability with the three-speed Torqueflite transaxle. Transaxle case machining capability on the same transfer line as the three-speed transaxle case. A number of innovations contributed to the implementation of these requirements. Basic to the design is the closed-loop real-time electronic feedback control system which enabled the Ultradrive to become the only major production fully automatic transmission without any freewheel upshifts. In addition to the unique control system, a totally new gear train and clutch arrangement provides for optimal use of available vehicle space. Central to this new arrangement are two simple planetary gear sets and a unique means for application of clutch elements. While it became apparent in early design studies that a departure from the Simpson gear sets used in all current Chrysler Motors automatic transmissions was necessary to meet requirements, the choice over an equally space saving compound planetary set of the Ravigneaux type was made in favor of better integration with production experience and wider ratio coverage. A shared piston and return spring arrangement for application of the overdrive and reverse clutch elements provides not only for optimal use of space but also results in economic speed signal generation. The input speed signal for the transmission controller is generated by an integrally machined tooth configuration on the input hub. Sharing of reaction plates between two different sets of clutch elements contributes to meeting space requirements. The successful implementation of the design depended on a number of innovations in materials processing and manufacturing technology. Chief among these are laser welding of dissimilar steels, austempering of both cast iron and steel, and the wide use of stamping technology. All of theseare new to automatic transmission production at Chrysler Motors Corporation. TRANSAXLE CONFIGURATION The Ultradrive has a 3-axis, in-line construction with all ratio-changing elements on the main center line (Figures 1 and 2). These consist of five friction elements and two simple planetary gear sets. Only friction discs and plates are used in the five friction elements. All three input clutches share common disc splines, as do the two reaction clutches. A sharing arrangement between neighboring clutch 167 Downloaded from SAE International by North Carolina State Univ, Tuesday, September 18, 2018Figure 1 - Ultradrive Cross Section elements permits use of only four pistons, four return springs, four apply plates and three reaction plates for all five clutch elements. Input from the torque converter is fed to the input clutch assembly, which houses the underdrive, overdrive, and reve