An automatic gearbox in a lorry is a key component of any heavy goods vehicle, responsible for the efficient transfer of power from the engine to the wheels. The functioning of this mechanism differs significantly from the solutions used in passenger cars, – primarily due to the heavier loads and specific requirements of heavy haulage. Trucks have to cope with loads weighing up to several dozen tonnes, which requires a completely different approach to gearbox design.
In this article, you will learn:
- Gears in lorries – types of gearboxes used in heavy goods vehicles
- How many gears does a lorry have? – the number of gears in lorries
- A truck’s gearbox – how the gear-changing process works
- The gearbox in a lorry – design and principle of operation
Gears in lorries – types of gearboxes used in heavy goods vehicles
There are several basic types of gearboxes in lorries, each with its own unique features. Understanding the differences between them will help you better understand how the entire drivetrain works. The most common types of gearboxes in heavy goods vehicles are:
- manual gearboxes – a traditional solution requiring the driver to change gears manually;
- automated manual transmissions (AMT) – manual gearboxes fitted with systems that automate gear changes;
- automatic gearboxes – using a torque converter;
- dual-clutch transmissions (DCT) – offering fast and smooth gear changes.
Modern lorries are predominantly fitted with automated manual transmissions, which combine the advantages of traditional manual gearboxes (high efficiency, lower fuel consumption) with the convenience of automatic gear changes. Today, an automatic gearbox in a lorry not only ensures driving comfort, but also helps to optimise fuel consumption by keeping the engine in its most efficient rev range.
Choosing the right gearbox for a lorry depends on many factors, including the type of transport, the terrain on which the vehicle will be driven, and the driver's preferences. It is worth remembering that modern SCANIA gearboxes or DAF gearboxes are technically advanced designs that require specialist knowledge for servicing and repairs.
How many gears does a lorry have? – the number of gears in lorries
How many gears does a lorry have? This is a question often asked by people outside the transport industry. Unlike passenger cars, where 5 or 6 gears are standard, the number of gears in lorries is much higher. A typical gearbox in a lorry can have between 8 and even 18 gears . Such a large number of gears is due to the need to precisely select the gear ratio for the current driving conditions and vehicle load. This allows the engine to operate within its optimal rev range, which translates into:
- lower fuel consumption,
- less wear and tear on components,
- better performance when starting under load,
- greater driving comfort.
An additional element that affects the number of available gear ratios is the splitter and reducer. The gear splitter allows each gear to be divided into two smaller ranges, effectively doubling the number of available gear ratios. The gearbox, meanwhile, allows the transmission to operate in two ranges – high and low – which also increases the number of available gears. The number of gears in a lorry also depends on the manufacturer and the specific model of the vehicle – for example, SCANIA lorries are fitted with 12-speed gearboxes, whilst DAF vehicles have 16-speed gearboxes. The more gears there are, the more precisely the driver (or the automatic transmission) can adjust the gear ratio to the current road conditions. Modern gearbox control systems analyse many parameters, such as:
- the current speed of the vehicle,
- engine load,
- road gradient,
- driver's driving style.
This will Gears in a lorry are changed at the optimum moment, which contributes to the economical and efficient operation of the vehicle.
A truck’s gearbox – how the gear-changing process works
Changing gears in a lorry is a much more complex process than in a passenger car. Depending on the type of gearbox, this procedure can be carried out in different ways. In the case of manual gearboxes, the driver must perform all the actions related to changing gears themselves:
- press the clutch pedal;
- move the gear lever to the neutral position;
- if necessary, change the range of the divider or reducer;
- move the lever to the position corresponding to the selected gear;
- release the clutch pedal smoothly.
This process requires experience and sensitivity on the part of the driver, especially when driving with a heavy load. Gear changes in a lorry must be made at the right moment to avoid jerks and excessive wear on the drivetrain components. Modern lorries are increasingly equipped with automated gearboxes that select the gear change moment independently. These systems, such as Scania Opticruise and DAF TraXon, use electronics to control the gear shifting process. The on-board computer analyses the current driving conditions and selects the optimal gear ratio, which greatly facilitates the driver's work.
The correct operation of a gearbox in a lorry depends on regular maintenance and the use of appropriate consumables . Regular visits to authorised service centres, such as, SCANIA service or DAF servicing help to keep the gearbox in excellent technical condition for a long time.
The gearbox in a lorry – design and principle of operation
A truck gearbox is a complex mechanism consisting of many precisely fitted components. Its basic components are:
- clutch shaft (input shaft) – connected to the engine via a clutch;
- main shaft – on which the gears for the individual gears are mounted;
- output shaft – which transmits torque to the drive shaft;
- synchronisers – designed to facilitate smooth gear changes;
- control mechanism – enabling the selection of the appropriate gear ratio.
The principle of operation of a truck gearbox is based on the use of various combinations of gears to obtain the appropriate gear ratio. Each gear is a different pair of interacting gears, one of which is located on the main shaft and the other on the output shaft. A truck’s gearbox must be much more robust than in passenger cars. This is due to the fact that it transmits many times greater torque. For this reason, high-quality materials and advanced design solutions are used in them.
To ensure long and trouble-free operation of the gearbox, it is worth using original truck parts, parts from reputable manufacturers. For SCANIA and DAF vehicles, it is recommended to use dedicated SCANIA parts, and DAF parts parts that guarantee the highest quality and durability. The gears in a lorry are designed to enable the effective use of engine power in various operating conditions. The first gears provide a high gear ratio, which allows the vehicle to start from a standstill even with a very heavy load. In turn, the highest gears (often called overdrive gears) allow for economical driving at high speeds with low engine revs.
Modern gearboxes are increasingly integrated with other vehicle systems, such as retarders, engine brakes and stability control systems. As a result, they form a comprehensive solution that not only transfers power, but also assists braking and improves driving safety.
Knowing how a gearbox works allows for more conscious use of the lorry, which translates into lower operating costs and a longer service life for the entire drive system.