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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.

Allison Transmission and Castrol Industrial North America have teamed up to offer a new synthetic automatic transmission fluid specially formulated for heavy duty automatic transmissions. The new product is called TRANSYND™1 and is approved for use in all current transmission models in all current truck and bus applications. Allison's worldwide customers now have a new option when selecting transmission fluid. Customers may continue to choose from a wide variety of approved DEXRON®-III or Allison C4 quality fluids or they may elect to switch to TRANSYND™ and extend drain intervals. TRANSYND™ has been shown to be cost effective by reducing maintenance through extended drain intervals while providing superior performance. Benefits may be optimized in severe vocations such as transit fleets where there are more vehicles and fluid change intervals tend to be more frequent. Similar savings may also be achievable in general (lighter) duty vocations such as school buses, motor homes, etc.