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This laboratory presents a new step-automatic transmission fluid with enhanced friction durability and robustness for the Asian marketplace. This mineral-oil-based fluid also meets JASO M315-1A performance requirements on torque capacity, anti-oxidation, anti-wear, extreme pressure (EP), anti-aeration/foam control, copper corrosion and anti-rust performance. The fluid offers a JASO M349 low velocity friction apparatus (LVFA) durability lifetime of over 1100 hours. Moreover, this fluid maintains stable torque capacity during its entire LVFA durability lifetime, across the temperature range of 40 to 120 °C. Similarly, friction level changes with sliding speed are smaller than experienced by other commercial factory-fill ATFs. These critical performance features are due to a new fluid friction system approach, which may enable new types of transmission hardware or calibration.

This paper reports development of a new automatic transmission (AT) fluid (ATF) with enhanced durability for the Asian marketplace. The authors contend the new step-automatic transmission hardware, such as wet starting clutches, new friction materials, dual clutches and six- and seven-speed ATs, create the need for enhanced levels of friction durability from the ATF. The new challenge from such hardware for the fluid developer lies in simultaneously meeting more stringent wear, extreme pressure (EP), friction durability and torque capacity requirements. The new additive chemistry, when used in a mineral oil base fluid, is capable of 1000+ hours in JASO M349 LVFA durability testing, a 16-fold increase over the JASO M349 reference ATF Toyota T-III. This performance easily doubles that of the currently most durable Asian ATFs, while offering better anti-wear and EP performance.

1 Fluids for new generations of step-automatic transmissions must provide durable service under severe conditions in a variety of environments. Fluid degradation under severe stress can lead to changes in frictional properties, potentially resulting in undesirable noise, vibration and harshness (NVH) events. This paper describes the development of a new transmission fluid that delivers significant improvement in squawk durability. The formulation approach resulted in optimum friction characteristics that are essential to overcome stress-induced loss of friction and to reduce NVH. A factorial design of experiments was used in the development process to relate additive effects with friction characteristics of both fresh and aged fluids. Friction durability after laboratory aging was compared with friction characteristics and durability data obtained from field-aged fluids

Friction plate degradation and/or friction plate glazing has often been related to the loss of friction control in automatic transmissions. However, in JASO SAE No.2 and LVFA tests, friction material glazing has been found to not be a sufficient condition for the loss of anti-shudder performance or a reduction in torque capacity durability. Therefore, changes in automatic transmission fluid properties rather than changes to the friction surfaces would be expected to play a dominant role in controlling anti-shudder performance and torque capacity. Earlier theoretical studies have proposed that friction in wet clutches is a combination of boundary and hydrodynamic friction. Therefore, changes in these properties should control anti-shudder durability and torque capacity. In this paper, we confirm that boundary and thin-film friction contribute to friction measured in JASO SAE No.2 and LVFA tests.

In automatic transmission technology development the degradation of paper friction plates has often been considered a major failure mechanism by which transmissions lose their anti-shudder characteristics. One of the most common degradation processes for paper friction plates is known as glazing. In this study, we focus on the relationship between friction plate glazing and anti-shudder durability in the Japanese Automobile Standards Organization (JASO) low velocity friction apparatus (LVFA) rig test following the procedure M349-98. We also investigate the impact of used friction plates and used oil on torque capacity durability as measured by an SAE No. 2 machine following the JASO procedure M348-95. We find that friction plate glazing has no correlation with anti-shudder durability. A completely glazed plate can have long anti-shudder durability but a barely glazed plate can have short anti-shudder durability.

This paper reports its findings in three separate parts. First, a comparative study is made among existing commercial dual clutch automatic transmission fluids (DCTFs). Significant differences in fluid torque capacity, friction material compatibility and copper corrosion performance were found among the fluids. Second, both a new vehicle chassis dynamometer durability test and a SAE#2 durability procedure are offered, specifically designed for DCTs. A 2008 VW GTI did well in the severe 60,000 mile chassis dynamometer procedure. Third, a new DCT fluid is discussed.