What does the term "torque multiplication" refer to in automatic transmissions?

The term "torque multiplication" specifically refers to the capability of the torque converter within an automatic transmission to enhance the engine's torque output at low speeds. This happens because the torque converter harnesses the engine's rotational energy and, through a series of hydraulic mechanisms, allows for an increase in the amount of torque that is transferred to the transmission input.

At low speeds, the torque converter creates a greater difference in speed between the engine and the transmission, allowing it to multiply the torque. When the vehicle is in motion and power needs to be transferred more efficiently, particularly during starting or heavy acceleration, this increased torque output is vital for optimal performance.

The other concepts mentioned do not correlate with the definition of torque multiplication. While one option discusses reducing engine power, this is contrary to the idea of multiplication, which involves an increase. Another option mentions a decrease in torque at high speeds, which doesn't align with the fundamental principle of torque multiplication. Lastly, measuring transmission fluid viscosity relates to how fluids behave under different conditions, but it has no direct association with torque multiplication itself.