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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.

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.

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 order to prevent shudder in automatic transmissions, friction must decrease as the sliding speed between the friction plates in clutches decreases. Theoretical studies have shown that friction in wet clutches is a combination of boundary friction and the friction due to flow of fluid through the friction materials (thin-film friction). Therefore, these physical properties of oils should control the anti-shudder performance of automatic transmission fluids. Recently, we demonstrated that boundary and thin-film friction contribute to friction measured at low speeds in JASO SAE No.2 and LVFA tests. Two different friction materials are used in these tests and the relative effect of thin-film friction on low speed friction is greater in the JASO SAE No. 2 test than in the JASO LVFA test.

This report focuses on an extended investigation of the durability of Dual Clutch Transmission (DCT) fluids. The performance requirements of DCT fluids differ from those of traditional step automatic transmission fluids. For that reason, key performance lab tests are discussed in this paper. Friction durability is measured with a modified version of the JASO M348 SAE#2 friction plate test. In addition, results from a vehicle chassis dynamometer test are discussed. This test involves running a 2008 Volkswagen GTI for 60,000 dynamometer miles (42,000 cycles) of severe acceleration and high speed conditions. Finally, a new DCT fluid, which performs well in these tests, offers friction stability and superior wear protection of transmission hardware, when compared to the commercial reference fluid.

This study focused on two areas of interest to CVT fluid developers. The primary set of experiments investigated whether continuously variable transmissions (CVTs) and their conventional step-type automatic transmission counterparts stress their fluids differently. The investigation compared the push-belt CVT (PB-CVT) in a '98 Nissan Bluebird to the General Motors (GM) Hydra-Matic 4L60 (four-speed) automatic transmission. Chemical, physical and performance comparisons of fresh and used fluids revealed the fluid stresses from the Nissan Bluebird CVT were similar to those from the 4L60 transmission. A second set of tests probed the question of how well results from two standard steel-on-steel friction bench tests correlate to CVT dynamometer (belt box) findings. The bench test models captured about half of the critical trends in the belt box data, as evidenced by prediction R2 values in the 0.5 to 0.7 range.

This study focused on steel-on-steel friction and wear in continuously variable transmissions (CVTs) that employ a push-belt design (PB-CVTs). The investigation considered commercial vehicles, represented by the Nissan Bluebird, along with a motored belt-box test that used the Ford P811 variator system. In addition, the authors employed the Falex block-on-ring bench test apparatus to measure both steel-on-steel friction and wear. The goal of the study was to investigate critical wear phenomena that occur in vehicle (field) use under severe conditions.

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.

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.