The gearbox provides a selection of gears for different driving conditions from climbing a hill, or cruising on level surfaces. The lower the gear, the slower the road wheels turn in relation to the engine speed. Internal combustion engines run at high speeds, so a reduction in gearing is necessary to transmit power to the drive wheels, which turn much more slowly.
Modern cars with manual transmissions have four or five forward speeds and one reverse, as well as a neutral position. The gearbox is the second stage in the transmission system, after the clutch. It is usually bolted to the rear of the engine, with the clutch between them.
The most popular design is the constant mesh gearbox. It has three shafts and the input shaft, the lay shaft and the main shaft, which run in bearings in the gearbox casing. The gear lever, operated by the driver as you as the driver of the Vehicle/Car, is connected to a series of selector rods in the top or side of the gearbox. The selector rods lie parallel with shafts carrying the gears.
When the driver selects a gear, matching cone shaped friction surfaces on the hub and the gear transmit drive, from the turning gear through the hub to the shaft, synchronising the speeds of the two shafts. In the time it takes to locate itself, the speeds of the shafts have been synchronised, so that the driver cannot make any teeth clash.
The synchrony is said to be unbeatable
as its build to perfection of the gearing system
as long as you match your gears to the right ratio.
Because of the large number of parts inside an automatic gearbox, some faults may be caused by more than one component. The first check should always be on the transmission fluid level and its condition and if it is all right, then you will need to check the other parts.
With the engine running and both the engine and transmission properly warmed up apply the foot brake firmly, select the lowest gear and fully depress the accelerator pedal so that the engine rev up keep it going until the revs
stop rising. Using an accurate rev counter, make a note of that engine speed called the stall speed. Release the accelerator and return the selector to neutral. Do not hold the transmission in the stalled condition for more than ten seconds or you may cause serious damage.