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19. Juli 2009

Hytrel helps resolve “baffling” design challenge

A unique approach to integrating a sealing and baffle function in GM’s 6T40 and 6T45 transversely mounted six-speed automatic transmissions helps condense packaging space and enable better clutch and transmission durability.

The integrated baffle and seal lip assembly, made of DuPont Hytrel thermoplastic polyester elastomer, is located in the torque transfer case and is designed to reduce oil aeration, provide a seal that limits fluid from flooding the chain while ultimately enabling transmission fluid fill for life. The one-piece, flexible component significantly reduces overall cost because it avoids the use of costly multi-step production and assembly processes, which were typically metal stampings or plastic carriers with a rubber bead.
Although Hytrel is not typically considered for transmission applications, it proved to offer the right balance of flexibility and stiffness despite temperature extremes to fit the complex geometries of the transfer case while resisting swell when exposed to oils, aliphatics and aromatic solvents, says the company. Two years in development saw tooling iterations and material upgrades to optimise performance for service temperatures that cycle between -40°C to +140°C. The team extensively used the Troy-based DuPont Automotive Application Development Center to test materials, various processes and tools. Now in production, the part is manufactured by Chunil Engineering in Korea and CWB Group in China.

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