Evaluating the Effect of Fluids on Automatic Transmission Piston Seal Materials 620231
A brief review of the testing of automatic transmission fluid for compatibility with seals is presented. The total immersion test used in fluid qualification, while apparently effective in predicting the compatibility of fluids and seals in service, does not correlate well with transmission tests with respect to hardness change of piston seals. The Dip-Cycle Test, developed to overcome this limitation, is a procedure for alternately immersing seal specimens in the test fluid and suspending them in the hot air-fluid vapor atmosphere above the fluid. Correlation of the Dip-Cycle Test with transmission piston seal results is much improved over that with the total immersion test.
It is the purpose of this paper to review these developments and to present an improved test procedure (dip cycle test) for evaluating the effect of fluids on transmission piston seal materials.