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The need for efficient space utilization has provided a framework for the design of a 248mm family of torque converters that supports a wide choice of engine and transmission combinations. The axial length of the part and its weight have been substantially reduced while the performance range has been broadened without degradation of efficiency. The new converter operates in an expanded slipping clutch mode. It significantly contributes to the performance and fuel economy improvements of related vehicles. To meet the cost target, the comprehensive lineup and the resulting complexity have required a high level of component interchangeability. During the design phase, the manufacturing core competencies were scrutinized and process redundancies eliminated, both resulting in optimization of material selection and applicable technology.

A wet multi-plate clutch, designated as the “starting clutch”, is used to replace the torque converter in the automatic transmission in order to improve vehicle fuel economy. The transmission ratio spread must be increased to compensate for the torque multiplication of the torque converter and avoid penalizing the 0-60 mph acceleration performance. The main challenge of this concept is the control of the starting clutch to ensure acceptable vehicle drivability. This paper describes the system of a five-speed starting clutch automatic transmission vehicle and shows vehicle test results. Vehicle test data show that (i) the fuel economy benefit of the starting clutch is significant, and (ii) a starting clutch transmission can be designed to equal or better the 0-60 mph acceleration performance of a torque converter transmission by proper selection of the gear ratios.

THIS description of the hydraulic control used with the hydra-matic transmission reveals how the control operates to change ratios under power without direction from the driver. The control's pattern of automatic shifting for ordinary, high-range driving has been selected as the best compromise between top performance and low ratio of engine noise to wind noise. The control's low range shifts gears according to performance dictates alone, furnishing greater power for extreme conditions at low speeds and enabling the driver to use his engine as a brake on steep descents. Heart of the control system is a double hydraulic governor, sensitive both to car speed and throttle opening. THIS paper, as well as the two that follow, one by Messrs. Nutt and Smirl and the other by Mr. Kimberly, make up a symposium on automatic transmission components presented at the 1947 SAE Summer Meeting.

In recent years, the slip lock-up mechanism has been adopted widely, because of its fuel efficiency and its ability to improve NVH. This necessitates that the automatic transmission fluid (ATF) used in automatic transmissions with slip lock-up clutches requires anti-shudder performance characteristics. The test methods used to evaluate the anti-shudder performance of an ATF can be classified roughly into two types. One is specified to measure whether a μ-V slope of the ATF is positive or negative, the other is the evaluation of the shudder occurrence in the practical vehicle. The former are μ-V property tests from MERCON® V, ATF+4®, and JASO M349-98, the latter is the vehicle test from DEXRON®-III. Additionally, in the evaluation of the μ-V property, there are two tests using the modified SAE No.2 friction machine and the modified low velocity friction apparatus (LVFA).

This paper assesses the potential for car and light truck fuel economy improvements by 2010-15. We examine a range of refinements to body systems and powertrain, reflecting current best practice as well as emerging technologies such as advanced engine and transmission, lightweight materials, integrated starter-generators, and hybrid drive. Engine options are restricted to those already known to meet upcoming California emissions standards. Our approach is to apply a state-of-art vehicle system simulation model to assess vehicle fuel economy gains and performance levels. We select a set of baseline vehicles representing five major classes - Small and Standard Cars, Pickup Trucks, SUVs and Minivans - and analyze design changes likely to be commercially viable within the coming decade. Results vary by vehicle type.

TURBOGLIDE is the deluxe automatic transmission of the General Motors Chevrolet. One of its most important features is that its performance ratio is available at any throttle position, enabling control of torque ratio and engine output by the throttle pedal. The system includes a five-element torque converter, pump, three turbines, and the dual stator. The entire installed unit weighs 148 lb, a result of the general arrangement and the use of aluminum in the case and bell housing. The authors discuss the basic operating principle of the transmission, the arrangement, performance, torque distribution, control system, and valve body.

The 45RFE is a new generation electronically controlled rear wheel drive automatic transmission. It employs real-time feedback, closed-loop modulation of shift functions to achieve outstanding shift quality and to meet demanding durability goals. It uses no shift valves; all friction element applications are effected with high-flow electro-hydraulic solenoid valves. A unique gear train arrangement of three planetary carriers allows all sun gears and annulus gears to have the same number of teeth respectively and use a common pinion gear in all carriers, resulting in significant manufacturing simplification. The three-planetary system is designed for four forward ratios of 3.00, 1.67, 1.00 and 0.75 and one reverse gear ratio equal to the low gear ratio. A fifth ratio of 1.50 is used only in certain kick-down shift sequences for highway passing. A sixth forward ratio, an additional overdrive ratio of 0.67, is available in the hardware.

The 45RFE is a new generation electronically controlled rear wheel drive transmission. It employs real-time feedback, closed-loop modulation of shift functions to achieve excellence in shift quality and to meet severe durability goals. The 45RFE uses no shift valves; all friction element applications are effected with high-flow electro-hydraulic solenoid valves. A unique gear train arrangement of three planetary carriers allows all sun and annulus gears to have identical numbers of teeth and to use common pinion gears in all carriers. This results in substantial manufacturing simplification. The three-planetary system is designed for four forward ratios of 3.00, 1.67, 1.00 and 0.75 and one reverse gear ratio equal to the low gear ratio. A fifth ratio of 1.50 is used mainly in certain kick-down shift sequences for highway passing. A sixth forward ratio, an additional overdrive ratio of 0.67, is available in the hardware.

As a result of raised awareness regarding the proliferation of individual OEM recommended ATFs, and discussion in various forums regarding the possibility of ‘universal’ service fill fluids, it was decided to study how divergent individual OEM requirements actually are by comparing the fluids performance in industry standard tests. A bench-mark study was carried out to compare the performance of various OEM automatic transmission fluids in selected industry standard tests. All of the fluids evaluated in the study are used by certain OEMs for both factory and service fill. The areas evaluated included friction durability, oxidation resistance, viscosity stability, aeration and foam control. The results of this study are discussed in this paper. Based on the results, one can conclude that each ATF is uniquely formulated to specific OEM requirements.

Current engine development processes typically involve extensive steady-state and simple transient testing in order to characterize the engine's fuel consumption, emissions, and performance based on several controllable inputs such as throttle, spark advance, and EGR. Steady-state and simple transient testing using idealistic load conditions alone, however, is no longer sufficient to meet powertrain development schedule requirements. Mapping and calibration of an engine under transient operation has become critically important. And, independent engine development utilizing accelerated techniques is becoming more attractive. In order to thoroughly calibrate new engines in accelerated fashion and under realistic transient conditions, more advanced testing is necessary.

Engine mount tuning is a multi-disciplinary exercise since it affects Idle-shake, Road-shake and powertrain noise response. Engine inertia is often used as a tuned absorber for controlling suspension resonance related road-shake issues. Last but not least, vehicle ride and handling may also be affected by mount tuning. In this work, Torque-Roll-Axis (TRA) decoupling of the rigid powertrain was used as a starting point for mount tuning. Nodal point of flexible powertrain bending was used to define the envelop for transmission mount locations. The frequency corresponding to the decoupled roll mode of the rigid powertrain was then adjusted for idle-shake and road-shake response management. The TRA decoupling procedure, cast as a multi-objective optimization problem, was applied to a body-on-frame sport-utility vehicle powertrain system. The process outlined in this work was verified by exercising a fullvehicle finite element model.

A wet multi-plate clutch, designated as the “starting clutch”, and a two-speed simple planetary gearset are used to replace the torque converter in the 4T60-E automatic transmission in order to study the potential improvement of vehicle fuel economy without sacrificing 0 - 60 mph acceleration performance. The starting clutch and the two-speed simple planetary gearset are designed to fit in the torque converter compartment. This paper describes the modified five-speed 4T60-E starting clutch automatic transmission system and provides vehicle test results to demonstrate its fuel economy and 0-60 mph performance potential.

General Motors introduced a family of small front wheel drive six speed automatic transmissions for the 2008 model year. The family currently has two variants: 6T40 and 6T45, which cover a range of vehicles from small & compact cars to small SUVs and handle engines torque capacities up to 240 Nm Gas(280 Nm Diesel) & 315 Nm Gas (380 Nm Diesel) respectively. The 6T40/45 transmissions replace GM traditional four speed automatic wrap around transmissions 4T40/45. The wrap around transmissions have Torque Converter, Pump & Controls on the engine axis and the rest of the transmission content on the output axis. The 6T40/45 have an on-axis architecture with majority of the transmission content on the engine axis and final drive & differential on the output axis. The 4T40/45 have input chain transfer whereas the 6T40/45 have an output chain transfer.

An impinging-flow based methodology of enhancing the heat transfer in the grooves of a lockup clutch is proposed and studied. In order to evaluate its efficacy and reveal the mechanism, the three-dimensional flow within the groove was solved as a conjugate heat transfer problem in a rotating reference frame using the commercial CFD code FLUENT. The turbulence characteristics were predicted using k-ε model. The comparison of cooling effect was made between a simple baseline groove pattern and a typical flow-impingement based groove pattern of the same groove-to-total area ratio in terms of heat rejection ratio, maximum surface temperature, and heat transfer coefficient. It is found that more heat can be rejected with the impinging-flow based groove from the friction surface than with the baseline while the maximum surface temperature is lower in the former case.

A global thermal model of a vehicle powertrain is used to quantify how different engine design and powertrain calibration strategies influence the performance of a vehicle heating system. Each strategy is evaluated on its ability to improve the warm-up and heat rejection characteristics of a small-displacement, spark-ignition engine while minimizing any adverse effect on fuel consumption or emissions. An energy audit analysis shows that the two strategies having the greatest impact on heating system performance are advancing the spark and forcing the transmission to operate in a lower gear. Changes in head mass, exhaust port diameter, and coolant flow rate influence the coolant warm-up rate but have relatively little effect on steady state heat transfer at the heater core.

Low frequency torsional vibrations can be a significant source of objectionable vehicle vibrations and in-vehicle boom, especially with changes in engine operation required for improved fuel economy. These changes include lower torque converter lock-up speeds and cylinder deactivation. This paper has two objectives: 1) Examine the effect of increased torsional vibrations on vehicle NVH performance and ways to improve this performance early in the program using test and simulation techniques. The important design parameters affecting vehicle NVH performance will be identified, and the trade-offs required to produce an optimized design will be examined. Also, the relationship between torsional vibrations and mount excursions, will be examined. 2) Investigate the ability of simulation techniques to predict and improve torsional vibration NVH performance. Evaluate the accuracy of the analytical models by comparison to test results.

An advancement in traction control has entered the marketplace this year with the debut of the 1999 Jeep® Grand Cherokee equipped with the Quadra-TracII or Quadra-Drive four wheel drive systems. The new technology that is at the heart of these systems is the progressive coupling. A new passive adaptive traction control device that utilizes much of the hardware normally associated with automatic transmissions but applied to enhance traction. In the following report the function of progressive coupling will be described along with design characteristics and parameter recommendations.

The new Allison M6600 and M9600 transmissions incorporate continuous improvement items to achieve greater robustness in terms of reliability and durability. This was partially accomplished by incorporating components from higher - capacity transmissions into current products with minimal redesign and tooling. A key life factor for all transmission components is adequate lubrication and cooling, and improvements in this area were accomplished by decreasing restrictions and better utilization of oil that was previously exhausted to sump. The new transmission models have further enhancements to clutch life through improved control of clutch torque and slip times. These clutch improvements were developed through the use of improved computerized evaluation techniques utilizing lap-top computer programs. Also, a transmission -mounted floating-caliper, disc type park brake with integrated controls is being evaluated as a possible replacement for the current drum-type brake.

The International Lubricant Standardization and Approval Committee (ILSAC) ATF subcommittee members have compared the two oxidation bench test methods, Aluminum Beaker Oxidation Test (ABOT) and Indiana Stirring Oxidation Stability Test (ISOT), using a number of factory-fill and service-fill ATFs obtained in Japan and in the US. In many cases, the ATFs were more severely oxidized after the ABOT procedure than after the same duration of the ISOT procedure. The relative severity of these two tests was influenced by the composition of the ATFs. The bench test oxidation data were compared with the transmission and the vehicle oxidation test data.

THIS paper describes the development of a truck automatic transmission, from a statement of broad objectives through the growing pains, to road testing of the final product. Emphasis is placed upon original thinking that led to the decision to undertake such a project, compromises that suggested themselves throughout the various stages, and features tried and found wanting as well as those retained. The finished product is described full though not in detail, stress being placed upon interesting and novel design features.