This SAE Recommended Practice is intended as the definition of a standard test, but may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 6000 r/min Stepped Power Test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 6000 r/min and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a. Friction Material b. Fluid c. Reaction Plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490 SAE No. 2 Friction Test Machine PVT Test.
It has been found that the current described pressure plate design can influence the results by creating a hydraulic cushion during operation. Installation of oil relief holes eliminates this possibility. Oil relief holes have become the defacto standard for many test labs running friction plate or transmission fluid testing. The current release level of the specification had several instances of possibly confusing formatting. One change was necessary in view of safety related changes to the inertia confinement vaults.