Development of Revised DEXRON®-III Elastomers Test

General Motors (GM) currently uses about 1000 different seals for manufacturing all of its automatic transmissions worldwide. In order to assure that these seals function correctly in service, a method of measuring seal performance with service fill automatic transmission fluids (ATFs) has to be specified. Along with this measure, a pass/fail criterion for the evaluation of seal performance is implemented. Due to the large number of seals that are utilized, it would be impractical to test each one with every fluid that is submitted for GM DEXRON^®-III and/or Allison C4 certification. It is also very difficult to use production seals in testing, due to the irregular shapes and material combinations, which make measurement of the seal material properties difficult. Therefore, a revised test will be included in the DEXRON^®-III and Allison C4 service fill specifications to evaluate the compatibility of service fill ATFs with a representative sample of seal materials used in production. This work describes how a group of ten representative materials was selected and referenced in order to define the GM service fill elastomers test for current and future DEXRON^® and C4 specifications.