Automotive gearboxes prime goal is to: a) expand the workable range of the IC engine (1000-5000rpm for Diesel, 1000-9000 - at best - for NA petrol, turbochargi

Automotive gearboxes prime goal is to: a) expand the workable range of the IC engine (1000-5000rpm for Diesel, 1000-9000 - at best - for NA petrol, turbocharging dials it down) b) solve the zero-to-low rpm problem that causes stalling due to nonexistent torque It results in a complex device where many parts are still spinning even on the non-engaged gear. Look at a cut out of a manual transmission. The irony is that an epicyclic automatic transmission is mechanically efficient, up to the torque converter which uses fluid coupling. Efficiency is a secondary goal to the ones above, without which the car would be useless.