Evaluating Tribology of Synchronizers for Today's Manual Transmissions

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Evaluating Tribology of Synchronizers for Today's Manual Transmissions

Bouffet, Alain

Manual transmissions are a common source of complaint from car drivers because of poor or hard shifting. For that reason, OEM pay increasing attention to the friction properties of the synchronising elements. There is a very limited range of standardised equipment for synchroniser performance evaluation on the market. Testing conditions in this equipment does not always match today's gearbox operating environment, particularly in terms of dynamic performance.Synchroniser Friction testing has been re-considered at ETSm with these new requirements in mind and practical solutions applied to produce a new rig with high dynamic performance and low operational cost.Synchronizer friction on this machine did particularly stress endurance wear and synchroniser sticking during the running-in phase on a reference brass synchronizer. Impact of the transmission lubricant formulation on initial friction coefficients has been studied and indicated more effect from base oil viscosity than from the Gear Oil performance package itself. Synchroniser design and technology has the strongest effect on overall friction behaviour and friction modifier is the most active component in lubricant formulation.