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The advent of the dual clutch transmission, which combines the performance advantages and hardware systems of both manual and conventional automatic transmission designs, has led to the development of new lubricant technology. A dual clutch transmission lubricant requires a new, specialized additive technology to meet the unique, often competitive, requirements of the different elements of the hardware system: specific clutch performance requirements related to the wet clutches along with high load-carrying and thermal stability associated with the manual transmission. We report the development of specialized lubricant technology that can be tailored to the specific requirements of the next generation, dual clutch transmissions.

Interactions between automatic transmission fluid (ATF) components and composite friction materials and their effect on friction system performance continues to be an active area of interest to the automotive industry. A more fundamental understanding is needed of how base fluids, ATF additives, friction materials, and transmission design interact to produce the observed transmission system performance and durability. We herein report results from investigations carried out using a relatively thermo-oxidatively stable polyalphaolefin (PAO) base fluid treated with components representative of several additive types we previously reported to have significant negative effects on frictional performance. Secondly, we investigated a conventionally refined 150 N base oil treated with a calcium sulfonate detergent previously shown to improve friction performance.

Automatic transmission clutches are complex tribological systems. Frictional performance is controlled by the interaction of base fluids, additive components, composition clutches, and steel reaction plates with varying energy inputs and thermal stresses in an oxidizing environment. This paper, rather than addressing fully formulated fluid performance in such a system, takes a more fundamental approach where the number of system variables is reduced and the relative effects of formulation variables on system performance can be better examined. Relationships among observed friction performance, system oxidation, friction member condition, and representative performance additives are explored using a synthetic base fluid and a conventionally refined mineral base fluid.