Wiktionary
vb. 1 To change the gear by which motion is transmitted from a powered shaft to another shaft, especially in a motor vehicle. 2 (context idiomatic English) To change pace or mode of operation.
Usage examples of "shift gears".
The thought of escape passed quickly once the car began to move and he became fascinated watching Lepage shift gears.
By then he'd cooked up a couple new schemes anyway and he was anxious to shift gears.
Why should I trust my life to some beardless boy who barely knows how to shift gears?
He had to shift gears frequently to navigate the minor hills and dales of this benthic terrain, for he was tired.
Cassie started to say something, stopped, then seemed to shift gears.
For a moment it seemed that Ira planned just to sit there, but then she heard him shift gears and drive on.