pinion and ring gear vs pinion and crown wheel

pinion and ring gear and pinion and crown wheel both are nouns.

Word	Noun	Adjective	Verb	Adverb
pinion and ring gear	Yes	No	No	No
pinion and crown wheel	Yes	No	No	No

As nouns, pinion and ring gear and pinion and crown wheel are synonyms defined as:

pinion and ring gear and pinion and crown wheel: gears that mesh at an angle

Other synonyms of pinion and ring gear include bevel gear.

pinion and ring gear (noun)	pinion and crown wheel (noun)
gears that mesh at an angle	gears that mesh at an angle