Formulating automatic transmission fluids (ATFs) can pose some diverse challenges. The friction response should ensure a smooth engagement process with no shudder in the automatic transmission. Friction, as a function of velocity, must show a smooth and positive/plateau curve as velocity increases in the μ−v plots. In this study, the friction behaviour of some basic additive systems for ATFs was assessed by using a variable speed friction test (VSFT) rig. The test was used to mimic the clutch engagement process and to evaluate the friction response of different formulations. The focus was anti-shudder properties of the designated formulations. A new method of evaluating VSFT results was developed to assess the overall ATF friction behaviour in conjunction to the common friction—velocity curve analysis. X-ray photoelectron spectroscopy was used to check the different surface conditions before and after the test.
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