gearbox vs transmission

gearbox

noun
  • That part of a car's transmission containing the train of gears, and to which the gear lever is connected. 

  • An enclosed gear train. 

transmission

noun
  • An assembly of gears through which power is transmitted from the engine to the driveshaft in a motor car / automobile; a gearbox. 

  • The fact of being transmitted. 

  • Something that is transmitted, such as a message, picture, or a disease; the sending of such a thing. 

  • The passage of a nerve impulse across synapses. 

  • The passing of a communicable disease from an infected host individual or group to a conspecific individual or group. 

  • The right possessed by an heir or legatee of transmitting to his successor(s) any inheritance, legacy, right, or privilege, to which he is entitled, even if he should die without enjoying or exercising it. 

  • The act of transmitting, e.g. data or electric power. 

How often have the words gearbox and transmission occurred in a corpus of books? (source: Google Ngram Viewer )