begin to move or act differently, usually more rapidly
This expression derives from literally engaging a different gear of a motor vehicle in order to alter its speed. Compare with in gear (with a gear engaged and so ready for action) and its opposite out of gear. To move up a gear means literally change to a higher gear. The phrase is often used figuratively to mean put more effort into an activity.
RELATED IDIOMS :
give someone the gears
harass or pester someone – Canadian
1989 - Guy Vanderhaeghe – Homesick - Whenever Daniel gave him the gears about overdressing, the old man grew sulky and grouchy.