Friction Characteristics of DEXRON®-III Automatic Transmission Fluids

The friction characteristics of several DEXRON®-III automatic transmission fluids were examined in a variety of friction tests. These evaluations included tests with SAE No. 2 Friction Machines using either Band or Plate heads, breakaway friction tests, and low-sliding speed friction tests. The effect of bulk fluid temperature on friction performance was examined in band tests and in breakaway tests using the plate clutch apparatus. The DEXRON®-III fluids were compared to the previous generation automatic transmission fluids. Results showed that the DEXRON®-III fluids exhibited more desirable friction characteristics; for example, with the DEXRON®-III fluids in the band machine, dynamic friction remained stable during sustained operation at high temperature, whereas with DEXRON®-IIE fluids, dynamic friction decreased as much as 25%. Band tests and breakaway friction tests at various temperatures showed fluid friction characteristics and durability to be sensitive to bulk fluid temperature, but with the DEXRON®-III fluid being less sensitive than the DEXRON®-IIE fluid.