Introduction:
The purpose of a transmission is to adjust the engine speed and thus the available engine torque and power to different driving conditions. This can be during acceleration or deceleration, transporting a heavy load, driving uphill or downhill, and changes in air and rolling resistance that can occur while driving. Shifting to a more favorable gear in these different conditions often leads to better fuel economy and more torque and power.
In a low gear (such as second gear), more engine torque is available than in a higher gear (such as fourth gear). This is because the crankshaft of the engine makes more revolutions in second gear and accelerates much faster than in a higher gear. Therefore, it is wiser not to drive in too high a gear when carrying a heavy load, such as a caravan, especially in the mountains.
Between the engine and the transmission is the clutch which consists of a clutch disc, a pressure plate, and a release bearing. By pressing the clutch pedal, the pressure plate is operated via a cable. In a hydraulic clutch, a fluid is transferred from one cylinder to another by means of two clutch cylinders. a0
Below is a block diagram showing how the drive from the engine to the wheels is achieved in front-wheel, rear-wheel, and all-wheel drive. For more information, see the page types of drive.
Single and Double Reduction:
Manual transmissions are divided into two groups, namely single and double reduction. Reduction is another term for transmission. So it actually means “single and double” transmission. Below is shown what is meant by it.
Single Reduction
The gears of the input and output shafts are directly connected. a0
A: Input shaft (input shaft, from the engine)
B: Output shaft (main shaft)
Double Reduction
First gear is engaged; the driving forces in first gear go from A to B and from C to D.
A force is applied to gear A via the input shaft. This gear is directly connected to gears B, D, and E. Since first gear is engaged, the synchronization device couples the output shaft to gear D (see blue arrows). From gear B, the driving forces exit the transmission through the output shaft. The output shaft drives the differential, which may be inside the transmission (in front-wheel drive cars) or may be mounted elsewhere as in a rear-wheel drive car. More is explained on this later on this page.
A: Gear input shaft a0(input shaft, from the engine)
B, C & E: Gears on the secondary shaft
D & F: Gears on the output shaft (main shaft)
Second gear is engaged. The synchronization device is disconnected from gear D and coupled to gear F (see blue arrows). At that moment, gear D still rotates, but is not coupled to the output shaft. Gear F is, so the driving forces now go from A to B and from E to F.
Since gears C and E have different dimensions, the gear ratios have changed. This results in a drop in engine speed after coupling at the same vehicle speed.