carmaker vs auto manufacturer

carmaker and auto manufacturer both are nouns.

Word	Noun	Adjective	Verb	Adverb
carmaker	Yes	No	No	No
auto manufacturer	Yes	No	No	No

As nouns, carmaker and auto manufacturer are synonyms defined as:

carmaker and auto manufacturer: a business engaged in the manufacture of automobiles

Other synonyms of carmaker include auto maker, automaker, car maker, car manufacturer.

carmaker (noun)	auto manufacturer (noun)
a business engaged in the manufacture of automobiles	a business engaged in the manufacture of automobiles