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There are many factors that can affect the service lifetime of a lubricant. In automobiles, one lubricant that has been heavily tested in recent years for fuel efficiency improvement and durability is axle lubricant. While a substantial amount of testing has been performed toward developing new axle lubricants to aid original equipment manufacturers to reduce warranty costs, improve Corporate Average Fuel Economy, and provide extended drain intervals, not as much testing has been documented to show some of the effects that different operating conditions have on these lubricants. The scope of this work is to bring to light some of the different parameters that affect axle lubricant.

A viscous damper is used as part of the automatic transaxle torque converter in some new passenger cars for improved driveability and fuel economy. A viscous silicone fluid is a critical component of the damper. Fluid viscosity-shear rate characteristics were determined in the laboratory for temperatures of 25 to 150 °C at shear rates from 400 to over 6000 reciprocal seconds. Using these data, and the dimensions of the viscous damper, a mathematical model was developed which predicts viscous damper output torque. Correlation between model predictions and actual measured torques from dynamometer tests was excellent. As a result, the mathematical model is useful for predicting viscous damper performance from measured fluid viscosity-shear rate characteristics. Also, since the model includes the critical viscous damper dimensions, it can be used for determining effects of damper design modifications on damper performance.

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).