vAccording to the number of sub-files of the transmission ratio, the final drive can be divided into single speed and two-speed type.
疑问:
what is sub-files of transmission ration?
出处:宋红英,汽车专业英语 3.5
推测来自中文:
按主减速器传动比档数分,有单速式和双速式;
谷歌搜索“sub-files of the transmission ratio”,仅此一条结果,表明英文根本没这种说法。