in/into high gear

:  rising or extending upward a great distance :  taller than average, usual, or expected

:  having a specified height or elevation :  tall

:  situated or passing above the normal level, surface, base of measurement, or elevation

:  at or to a high place, altitude, level, or degree

:  well, luxuriously

:  an elevated place or region: such as

:  hill, knoll

:  the space overhead :  sky

:  clothing, garments

:  movable property :  goods

:  equipment, paraphernalia

:  to provide (machinery) with gearing (see gearing 2)

:  to connect by gearing (see gearing 1)

:  to make ready for effective operation