Wet Friction Testing

The performance and durability of fluids and friction materials is an important aspect of transmission component testing. Greening’s experienced engineers and technical personnel help our clients obtain critical information as part of a component or system test program. Testing can be conducted under dynamic (inertia) stop, continuous slip (low speed / high torque), and static breakaway conditions on components such as torque converters, power take off units, synchronizers, transfer cases, clutch disks, one-way clutches, bands, and other transmission components. Other special capabilities include spin/loss and dynamic drag coefficient measurement.

An example of Greening’s technical involvement with the industry is a test procedure to precisely evaluate shudder properties of automatic transmission fluid (ATF) for continuous slip torque converters. We run the tests on a modified SAE No. 2 machine which simulates sliding speed, surface pressures, fluid temperatures and interfacial fluid flow conditions found in actual vehicles.

This test has been approved to be part of Ford’s MERCON® Qualification Program. The MERCON® specification applies to most models made by the Ford Motor Company, including the Ford, Lincoln and Mercury brands. We can characterize the effect of continuously varying interfacial speed on the friction behavior of a fluid clutch system.

Our pioneering contribution is acknowledged in SAE International’s technical paper #940821: “Prediction of Anti-Shudder Properties of Automatic Transmission Fluids using a Modified SAE No. 2 Machine.” The paper, published in 1994, was written by engineers from specialty chemical company Ethyl Petroleum Additives, now known as Afton Chemical.

GTL’s newest SAE No. 2 test machine utilizes Greening’s latest Dyna_Works™ software (Microsoft® Windows® based interface) and adds automated sequencing between high speed, low speed and static breakaway test modes, expanding Greening’s test capabilities.

Commonly used test procedures include:

  • SAE J2487 – 3600 r/min Stepped Power Test
  • SAE J2488 – 6000 r/min Stepped Power Test
  • SAE J2489 – Durability Test
  • SAE J2490 – µPVT Performance Test
  • SAE J2964 – Low Speed Mu Procedure