In order to understand how manual transmission works, we need to know what a car needs it for. That’s torque, and it makes the car move. The inclination of the road surface, the car’s weight and other engine characteristics combined dictate what amount of torque is necessary to smoothly drive along.
Engines by themselves are not constant-torque devices, and since we can’t drive an engine at constant speed, it needs to be attached to something that mechanically multiplies the torque to allow a smooth operation. And that is what a manual transmission does; it smoothes out the torque curve of the engine to permit the car to start off and to accelerate at a desired level. Then you are able to drive at the highest speed with the engine running at its most efficient level.
A manual transmission is made up of several shafts, like the input shaft, the output shaft, the layshaft and a reverse gear. All the gears are mounted on the shaft. Though there is no limit to the number of gears that a manual transmission can have, common practice limits them to 6 forward speeds. Each of these gears perfectly fits its counterpart on the layshaft. Each gear is cut with a number of teeth that allow it to produce a desired ratio, which creates torque multiplication. The gears in a manual transmission don’t move, except the reverse. All of them are in constant alignment with their counterparts.
Another important part of the manual transmission is the synchronizer, a bronze ring that sits next to the gear and helps create a friction that slows the speed of the assembly enough for the shift hub’s spline to grab the teeth from the synchronizer and gear sprocket.
Manual transmission is what allows the gear ratio between the engine and the drive wheels to change as the car speeds up or slows down. The reason we shift gears when driving is so the engine can stay below the redline and near the rpm band of its best performance. All the parts in a transmission are assembled with extreme precision, and the whole assembly sits in a pool of gear oil, so that you can drive without glitches. This is why we must treat the gearbox with respect, that is to say, we must learn how to properly use it in order to avoid causing big damage to the car’s engine.