gear lever vs mechanical device

gear lever and mechanical device both are nouns.

Word	Noun	Adjective	Verb	Adverb
gear lever	Yes	No	No	No
mechanical device	Yes	No	No	No

As nouns, mechanical device is a hypernym of gear lever; that is, mechanical device is a word with a broader meaning than gear lever:

gear lever: a mechanical device for engaging and disengaging gears
mechanical device: mechanism consisting of a device that works on mechanical principles

gear lever (noun)	mechanical device (noun)
a mechanical device for engaging and disengaging gears	mechanism consisting of a device that works on mechanical principles