Fuel economy is well known as the main driver for change in transmission and automatic transmission fluid (ATF) technology. This driver has led to the reduction in size and weight of transmission components and also advancements in transmission design. Some of the key transmission design changes include the addition of continuously slipping torque converter clutches, the increase in the number of speeds, the use of more thermally stable friction materials, and other refinements. Specific adjustments to improve ATF performance in these new transmission environments include: 1) reduced viscosity for lower churning losses and improved fuel economy; 2) high shear stability to ensure adequate fluid film thickness throughout the life of the vehicle; 3) high Viscosity Index (VI) oil characteristics for improved fuel economy; 4) improved gear and bearing protection due to lower viscosity; 5) higher static friction for improved clutch holding capacity; 6) higher dynamic friction for greater torque transfer performance; and, 7) long-term anti-shudder performance to enable aggressive use of controlled slip torque converter clutches for fuel economy.
We herein report the development of new ATF technology specifically designed to meet all seven of the ATF fluid performance areas mentioned. Extensive friction, oxidation, and wear data is presented along with information from field testing. Much of the friction testing involves the JASO LVFA (Low Velocity Friction Apparatus) measuring anti-shudder performance using graphitic-containing composite friction material, the modified JASO SAE No. 2 that measures torque capacity, the Ford Friction Durability test using either a paper composite or graphitic-containing composite friction material, the GM low speed friction test using woven carbon fiber plates, and the Ford Anti-shudder Durability test. The Ford Aluminum Beaker Oxidation Test (ABOT) test measures oxidation performance. Wear performance data of this new ATF technology entails shear stability, and a full transmission dynamometer test using a V-10 engine to establish gear protection properties.
The results of all of this testing show that the new AT technology can address all these major concerns in a single fluid that is superior to existing commercial AT fluids across the globe.