The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with high gear
A state of maximum activity, energy, or force. For example, His mind was in high gear as he studied for the medical exam, or The political campaign is finally moving into high gear. This expression alludes to the high gear of an engine transmission, used at the fastest speeds.