MANUAL TRANSMISSION

MANUAL TRANSMISSION

The purpose of a transmission is to multiply the engine’s turning effort or torque to allow the vehicle to move efficiently from a dead stop to highway speed. The driver controls a transmission manually or automatically.

The transmission helps the engine start the vehicle moving from a standstill and accelerate to road speed. The engine and transmission work as a team.

The drive wheels of the vehicle rotate to drive the vehicle. The twisting or turning effort is called torque. The engine develops torque. The problem is that the engine alone cannot develop enough torque to get the vehicle moving from a standstill. The engine needs help also during acceleration and hill climbing.

The torque that a typical gasoline engine can produce can be measured and plotted on a graph.

The unit of measurement for torque is expressed in Newton meters. The torque is shown at various engine speeds (revolutions per minute or rpm).

Different engines, of course, describe different curies, but they are all similar. At low engine rpm, torque is low. As engine rpm increases, torque increases up to a point in the rpm range at which the engine will have trouble taking in enough air and fuel. At this point the torque curve will begin to drop off. The transmission must work to overcome low torque at low rpm. The transmission at the lower gear trios allows the engine to pirate at higher speeds during low vehicle speeds so the engine can operate at, or near, its best torque range. The transmission’s job is torque multiplication: that is, to multiply the engine’s low initial torque to get the vehicle moving and to meet varying road conditions.