Search Results

Frictional characteristics of several automatic transmission fluids (ATF's) were evaluated in an SAE No. 2 Friction Machine adapted to the band clutch from a front-wheel-drive, three-speed automatic transaxle. The bench test apparatus subjects the band clutch to repeated engagements (24 000 in a 100-hour test period) at elevated temperature with representative clutch energy dissipation and lockup time, and with forced aeration of the fluid. Fluid frictional performance is judged from the level and stability of friction torque during the 24 000 clutch engagements. The test is repeatable and readily distinguishes fluids having different frictional characteristics. Fluid frictional behavior in the band machine is shown to reflect fluid effects on shift performance in an engine dynamometer, transaxle cycling test. Also, fluid effects determined in the cycling test are shown to match those obtained in a vehicle.

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%.