In what way does mechanical efficiency in gears affect output torque and angular velocity? Mechanical efficiency affects power which is the product of torque and angular velocity. Let's say we have a gearbox with a mechanical efficiency of 0.95, hence the output power is 95% of the input power, but how does this affect speed and torque? Is only the torque reduced by 5% or is it a combination of torque and speed reduction? Does this vary from system to system, for example, a worm drive differs from a bevel gear drive? I wish to design a gearbox whose input and output run at the same speed, however in between is a series of gears. Let's assume these gears have a resultant system efficiency of 0.9. My input and output has a theoretical gear ratio of 1:1 because I intend them to move at the same speed. As my system efficiency is 0.9, does this mean my output speed is no longer the same as my input speed so my gear ratio isn't 1:1 as designed? I am assuming this isn't the case as gears are timing devices, and what efficiency should affect is only torque.