The phrase "transmission shift" refers to the process of changing gears in a vehicle's transmission system. It involves shifting from one gear to another, which affects how power is transferred from the engine to the wheels. Full definition
The 6 - speed automatic transmission shifts smoothly at just the right time with no hesitation, though it costs a little in fuel economy. (bestride.com)
The computer is tuned for more aggressive transmission shift points, and the transmission itself is built for firmer and harder shifts. (en.wikipedia.org)