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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%.

The effects of automatic transmission fluid viscosity on the low-temperature performance of a front-wheel-drive transaxle were determined in a cold room maintained at a temperature of -20°F (-28.9°C), using both a cranking apparatus and a vehicle. Cranking and vehicle tests were conducted to determine the effects of fluid viscosity on the power required to crank a transaxle and on transaxle performance under low-temperature transient operation, respectively. Four automatic transmission fluids were tested, ranging in viscosity from 2 800 to 16 000 cP at -20°F. All test fluids contained the same additive package and were blended using the same types of base oils. Reducing fluid viscosity from 6 000 cP (current factory-fill) to 3 900 cP at -20°F reduced shift times by 10 percent, forward clutch engagement time by 25 percent, apply pressure rise times by 40 percent, and cranking loads by almost 40 percent.