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ATF Bulk Oxidative Degradation and Its Effects on LVFA Friction and the Performance of a Modulated Torque Converter Clutch
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English
Abstract
The friction behaviors of fresh and aged ATFs and a paper-based wet friction material were characterized using a low velocity friction apparatus (LVFA). Friction tests on 30 ml samples of ATF were used to characterize the friction durability of ATFs aged in test vehicles and in the Ford Aluminum Beaker Oxidation Test (ABOT). Oxidation test data gave stability rankings for the various ATFs which were consistent with limited vehicle experience. The procedure was applied to the analysis of results from a fleet test run with transmissions equipped with a modulated torque converter clutch. The test was aimed at characterizing friction degradation and shudder. Samples obtained from the test fleet were used to construct degradation profiles for two ATFs. The profiles showed no significant difference between the two ATFs in friction stability, consistent with the results of bench oxidation tests. However, an oil to air cooler was seen to provide some improvement. A friction coefficient - speed slope criterion was proposed as an indicator for an ATF prone to cause shudder. ABOT tests were carried out on one fluid at several different temperatures. Samples were withdrawn periodically and run in the LVFA. Time-temperature degradation profiles were constructed from the friction data and used to make quantitative predictions of friction degradation in the test vehicles. The results agreed well, supporting the idea that bulk oxidative degradation of ATF in service is a key factor in friction durability of modulated torque converter clutches.
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Authors
- P.A. Willermet
- G. K. Gupta - The Automatic Transmission Engineering Operations, The Ford Motor Company
- D. Honkanen - The Automatic Transmission Engineering Operations, The Ford Motor Company
- J. W. Sprys - The Automatic Transmission Engineering Operations, The Ford Motor Company
- D.G. McWatt - The Automatic Transmission Engineering Operations, The Ford Motor Company
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Citation
Willermet, P., Gupta, G., Honkanen, D., Sprys, J. et al., "ATF Bulk Oxidative Degradation and Its Effects on LVFA Friction and the Performance of a Modulated Torque Converter Clutch," SAE Technical Paper 982668, 1998, https://doi.org/10.4271/982668.Also In
References
- “The Application of Antioxidant Analysis to Transmission Fluid Testing” Willermet P.A. Mahoney L.R. Kandah S.K. Sever A.W. SAE paper 790016 1979
- “The Prediction of ATF Service Life from Laboratory Oxidation Test Data” Willermet P.A. Mahoney L.R. Kandah S.K. Sever A.W. SAE paper 801363 SAE SP-473 “Deterioration of Automotive Lubricants in Service” 1980
- “Prediction of Low Speed Clutch Shudder in Automatic Transmissions Using the Low Velocity Friction Apparatus” Watts R.F. Nibert R.K. “Engine Oils and Automotive Lubrication” Bartz W.J. Marcel Dekker, Inc. New York 1993
- “Slipping Torque Converter Clutch Interface Temperature, Pressure and Torque Measurements Using Inductively Powered Radiotelemetry” Throop M.J. McWatt D. G. SAE paper 970679 1997
- Ford Laboratory Test Method
- “The Aluminum Beaker Oxidation Test for MERCON‰ World-Wide Service ATF” Willermet P. A. Kandah S. K. SAE paper 881673 SAE Fuels and Lubricants Meeting Portland, OR October 10-13 1988
- “Interaction Between ATFs and Friction Material for Modulated Torque Converter Clutches” Guan J.J. Willermet P.A. Carter R.O. III Melotik D.J. SAE Paper 981098 SAE International Congress and Exposition Detroit, MI February 23-26 1998
- “Development of Automatic Transmission Fluid for Slip Controlled Lock-Up Clutch Systems” Kugimiya T. Mitsui J. Yoshimura N. Kaneko H. Akamatsu H. Ueda F. Nakada T. Akiyama S. SAE Paper 952348 1995