Which of the following power flows gives the maximum forward reduction in speed but the maximum increase in torque?

• A. Maximum forward reduction
• B. Minimum forward reduction
• C. Minimum forward overdrive
• D. Maximum forward overdrive

Answer: (A)

In a drive train, power is mostly conserved through gears, so torque and speed trade off depending on the gear ratio. A forward reduction means the output speed drops while the output torque rises, because the gear multiplies torque while dividing speed. The larger the reduction, the bigger the torque boost and the bigger the speed decrease. Therefore, the maximum forward reduction gives the greatest increase in torque at the cost of the greatest decrease in speed. The other options would either reduce torque less, or actually increase speed (forward overdrive), which lowers torque rather than raises it. So the best choice is the maximum forward reduction.