What are the parts of the truck called: analysis of the structure from the hood to the wheels

Trucks are complex engineering structures consisting of hundreds of parts, each of which performs its own function. Knowing the names and purposes of the main parts of a truck is critical not only for professional drivers, but also for fleet owners, mechanics, and even ordinary car enthusiasts who want to understand technology. Without this information, it is difficult to communicate with service technicians, buy spare parts, or understand what kind of breakdown is being discussed in the diagnostic report.

In this article we will analyze in detail all key components of the truck - from the engine and transmission to body elements and electrical equipment. You will learn not only the official technical names, but also the slang terms that truckers use. And diagrams and photographs will help you visually remember where everything is located. If you've ever been confused about terms like "driveshaft" and "axle shaft" or couldn't explain to a mechanic what exactly is creaking in the suspension, this guide is for you.

1. The main sections of the truck: what they are called and what they are responsible for

Any truck can be divided into three main parts, each of which includes dozens of smaller nodes. This division helps you quickly navigate the design and understand which system a particular part belongs to.

• 🚛 Chassis — this is the “skeleton” of the truck on which all other elements are attached. Includes frame, suspension, wheels, brake system and steering. It is the chassis that determines the load-carrying capacity and maneuverability of the vehicle.
• 🔧 Engine and transmission — the “heart” and “nervous system” of the car. This includes the engine itself, gearbox, clutch, driveshafts and axles. The power, efficiency and reliability of the truck depend on the condition of these components.
• 📦 Body and superstructure - the part that is in direct contact with the cargo. It can be a flatbed body, a van, a tank, a dump platform, etc. This also includes the driver’s cabin with its equipment.

It's interesting that in European trucks (for example, Volvo FH or Scania R) the cabin is often made into a separate module that can be tilted forward to access the engine. And in American (type Freightliner Cascadia) the engine is usually located under the cab and requires a special lift to service it.

2. Chassis parts: frame, suspension and wheels

The chassis is the foundation of the truck, on which its strength and load capacity depend. The main element here is frame, which happens:

• 🔩 Spar - two longitudinal beams (spars) connected by cross members. The most common type for trucks (e.g. KAMAZ or MAN TGS).
• 🏗️ Khrebtovaya - the central pipe to which all units are attached. Used in some military trucks and special equipment.
• 🚜 Frameless — the body is attached directly to the supporting base (typical for small trucks type Gazelle Next).

Attached to frame suspension, which happens:

• 🔄 Spring — a classic for trucks, reliable and easy to repair. Consists of steel springs (sheets) that soften impacts.
• 🌀 Pneumatic - uses air in cylinders for shock absorption. Provides a smooth ride, but is expensive to maintain (installed on Mercedes Actros or DAF XF).
• 🛢️ Hydraulic - rarely found on production trucks, more often on special equipment.

Wheels trucks also have their own specifics. For example, on multi-axis machines (such as Volvo FH16 750) are used twin wheels (or "twin") on the rear axles to distribute the load. And on mining dump trucks (for example, BelAZ) wheels can be as tall as a person!

Chassis element	Purpose	Typical faults
Frame spars	Supporting base for mounting units	Overload cracks, corrosion
Springs	Shock absorption and body support	Breakage of sheets, subsidence
Shock absorbers	Damping vibrations	Oil leak, loss of efficiency
Wheel bearings	Ensuring wheel rotation	Wear, play, overheating

3. Engine and its components: what is where

The engine is the most complex and expensive component of a truck. In modern cars they are mainly used diesel engines turbocharged, although there are also gasoline ones (for example, on small trucks type Ford Transit). Main parts of the engine:

• 🔥 Cylinder block - the “body” of the engine, where the cylinders, pistons and crankshaft are located. Made from cast iron or aluminum alloy.
• ⚙️ Cylinder head (cylinder head) - the upper part where the valves, camshafts and glow plugs are located (in diesel engines).
• 🌀 Turbocharger - pumps additional air into the cylinders to increase power. Often used in trucks variable geometry turbo (VGT).
• 🛢️ Fuel system - includes fuel injection pump (high pressure fuel pump), injectors and filters. Modern diesel engines use a system Common Rail.

One of the most vulnerable elements is diesel particulate filter (DPF), which cleans exhaust gases from soot. It requires regular regeneration (cleaning), otherwise the engine will go into emergency mode. B European trucks (for example, Scania or DAF) DPF is integrated into the exhaust system, and American (type Peterbilt) may not be available due to other environmental regulations.

In trucks with engines Euro-6 system is used SCR (Selective Catalytic Reduction), which injects urea (AdBlue) into the exhaust to neutralize nitrogen oxides. Without AdBlue filling, the engine will not start or will operate in limited mode.

What is an "engine brake"?

This is a system that uses engine resistance to slow the truck without using pads. It is activated by a button on the steering wheel and is especially useful on long descents to avoid overheating the brakes. In diesel engines it is realized through changing the valve timing or closing the exhaust valves.

4. Transmission: gearbox, clutch and driveshafts

The transmission transmits torque from the engine to the wheels. In trucks, it is more difficult than in cars, because you need to manage a large mass and several axles. Main components:

• 🔄 Clutch — connects and disconnects the engine with the gearbox. Used in trucks disc clutch with hydraulic or pneumatic drive. On heavy machines (for example, Volvo FH16) maybe double disc clutch to transmit more torque.
• ⚙️ Gearbox - usually in trucks mechanical (for example, ZF 16S 16 gears) or automated (type Opticruise from Scania). Less common are complete “automata” (for example, Allison on American trucks).
• 🔗 Cardan shafts — transmit torque from the gearbox to the axles. Long wheelbase trucks may have multiple universal joints with intermediate supports.
• 🚗 Transfer case - used in four-wheel drive trucks (for example, Ural or Unimog) to distribute torque between axles.

One of the most common problems in truck transmissions is synchronizer wear in the gearbox. This manifests itself as a crunching sound when switching, especially when cold. They also often fail input shaft bearings, which results in a howling sound.

Box type	Benefits	Disadvantages
Mechanical	Reliability, maintainability, low price	Difficulty controlling, driver fatigue
Automated (AMT)	Ease of control, fuel economy	Expensive repairs, sensitivity to overloads
Hydromechanical (automatic)	Smooth ride, comfort	High price, difficult to maintain

5. Axles, differentials and axle shafts: what turns the wheels

Axles are units that transmit torque from the transmission to the wheels. There may be several of them in trucks:

• 🔄 Drive axle — the one that receives torque from the box and spins the wheels. In most trucks, the rear axle is the drive axle, but in all-wheel drive vehicles (for example, MAZ-6317) all bridges can be leading.
• 🛣️ Steerable bridge - the front axle that turns the wheels. In some trucks (eg. Mercedes Arocs) he can also be the leader.
• 🚛 Support bridge - additional bridge to increase load capacity (for example, in three-axle dump trucks). Not leading and not controlled.

Inside the bridge is differential - a mechanism that allows the wheels to rotate at different speeds (for example, in turns). Often used in trucks lockable differential, which can be turned on to improve off-road performance.

Half shafts - these are the shafts that connect the differential to the wheels. They are:

• 🔧 Fully unloaded — support bearings are located on the bridge body, and the axle shaft transmits only torque (the most reliable option).
• 🛢️ Semi-unloaded — the bearing is installed on the axle shaft itself, which increases the load on it.

One of the most dangerous malfunctions in this system is axle shaft failure. If this happens while driving, the wheel may jam, resulting in loss of control. Therefore, when knocking on the bridge or vibrations I urgently need to go for a diagnosis.

6. Braking system: how the truck stops

The brake system of a truck is a set of mechanisms that must reliably stop a multi-ton vehicle. It consists of several subsystems:

• 🛑 Service brake system - main, used to stop. Usually in trucks pneumatic (compressed air presses on the brake pads).
• 🔄 Parking brake system - holds the truck in place. Often combined with work (for example, through spring energy accumulators).
• 🚨 Spare brake system — duplicates the working one in case of its failure.
• 🌀 Auxiliary braking system — retarder brake (for example, hydraulic or electromagnetic), which reduces the load on the main brakes.

Main elements of the brake system:

• 🔧 Brake pads and drums - more often used in trucks drum brakes (they are more reliable than disk ones under heavy loads), although on modern machines (for example, Volvo FH) can stand and disk.
• 🛢️ Compressor — pumps air into the pneumatic system. If it breaks, the brakes will stop working!
• 🌀 Receivers — tanks for storing compressed air.
• 📉 Brake force regulator — distributes the braking force between the axles depending on the load.

ABS (anti-lock braking system) mandatory in trucks since the 1990s. It prevents the wheels from locking when braking, which is especially important on slippery roads. In modern machines (for example, DAF XF) is used EBS (Electronic Braking System), which is integrated with ABS and improves braking control.

⚠️ Attention! If the air pressure in a truck with a Suddenly air brake system drops below 5 bar, stop immediately - this may result in complete loss of brakes. Most often to blame hose rupture or compressor malfunction.

7. Electrical equipment and cabins: comfort and control

A modern truck is not only about mechanics, but also about complex electronics. Main elements of electrical equipment:

• 🔋 Batteries - in trucks there are usually two of them (24V), since the starter and on-board network require a lot of power. For example, on Scania R450 the batteries cost 180-225 Ah.
• 🔌 Generator — charges batteries and powers the on-board network. The trucks use a generator with a capacity of 140-200 A.
• 💡 Lighting - turns on the headlights (often xenon or LED), dimensions, brake lights and additional spotlights.
• 📡 On-board electronics — ECU (electronic control units), sensors, diagnostic system (for example, FMS in Volvo).

The truck cabin is the driver's workplace, and its equipment greatly affects comfort. In modern machines (for example, Mercedes Actros or DAF XF) cabins are equipped with:

• 🛋️ Sleeping place (in long-range versions).
• 🌡️ Climate control (sometimes with a separate liquid fuel heater for overnight stays in winter).
• 📱 Multimedia system with navigation and communication.
• 🔧 Ergonomic seat with heating and air suspension.

One of the most common problems in electrical equipment is battery discharge due to current leakage. This can happen if you leave the headlights or refrigerator on in your bed. They also often fail voltage regulator relays, which leads to undercharging or overcharging of batteries.

8. Body and superstructures: types and features

The body of a truck determines its specialization. Main types:

• 📦 Flatbed body — a universal option for transporting bulk or piece goods. May have folding sides or an awning.
• 🚛 Van — closed body to protect the cargo from the weather. It happens isothermal (for products) or refrigerator (with refrigeration unit).
• 🛢️ tank — for transportation of liquids (fuel, water, chemicals). Can be made of aluminum, stainless steel or plastic.
• 🏗️ Tipper platform — for bulk cargo (sand, crushed stone). Has a hydraulic lift for unloading.
• 🚜 Special add-ons - for example, car transporters, timber trucks or concrete mixers.

The body is attached to the frame using brackets and stepladders. It is important to monitor the condition of the fasteners, since loosening them can lead to the body shifting or even tearing off (which often happens in an accident).

B refrigerators special attention is paid refrigeration unit. It could be:

• 🔥 Autonomous - with its own diesel engine (for example, Thermo King or Carrier).
• 🔌 Dependent — is powered by the truck’s electricity (less often, as it puts a lot of load on the generator).

⚠️ Attention! When transporting dangerous goods (for example, fuel or chemicals), the body must be certified and is equipped with special emergency valves and grounding. Violation of the rules can lead not only to a fine, but also to refusal of the insurance company to pay in case of an accident.

FAQ: Frequently asked questions about truck parts

🔧 Why do trucks use a pneumatic braking system rather than a hydraulic one?

Air brakes are more reliable for heavy vehicles for several reasons:

• Compressed air can be stored in receivers, which allows you to perform several brakes even if the compressor is faulty.
• The pneumatic system is less sensitive to overheating than hydraulics.
• Air brakes are easier to synchronize on multi-wheel drive vehicles (such as a trailer).

However, pneumatics require regular maintenance (checking for leaks, replacing the air dryer).

🚛 What are “twin wheels” and why are they needed?

Twin (or double) wheels are when two wheels are installed side by side on one axle. This is done for:

• Increased load capacity - weight is distributed over a larger area.
• Increases stability - reduces the risk of capsizing.
• Reducing pressure on the road (relevant for countries with axle load restrictions).

Cons: rolling resistance increases (fuel consumption increases) and it is more difficult to change tires.

⚙️ What is the difference between a Euro-6 engine and a Euro-5 engine?

Main differences:

• SCR system — in Euro-6, urea injection (AdBlue) is required to neutralize nitrogen oxides.
• Diesel Particulate Filter (DPF) — more stringent requirements for its effectiveness.
• Exhaust gas recirculation (EGR) system — in Euro-6 it is more advanced.
• Electronics - more sensors and stricter emissions control.

Euro-6 trucks are more difficult to maintain, but more environmentally friendly. In some countries (for example, in the EU), cars below Euro-6 are already prohibited for use.

🛠️ How often should you change the oil in a truck engine?

The frequency depends on:

• Engine type — for Euro-6 the interval is usually 60,000–100,000 km, for old engines (Euro-3) - 20,000–40,000 km.
• Operating conditions — when working in difficult conditions (dust, off-road conditions, frequent downtime), the oil is changed more often.
• Oil type - synthetic lasts longer than mineral.

It's important to keep track oil condition according to analysis (for example, at a service station), since its degradation may occur ahead of schedule due to low quality fuel or overheating.

🔋 Why do trucks have two batteries?

Two batteries (24V) are needed because:

• A truck starter requires a high starting current (especially in winter).
• The on-board network (lighting, refrigerator, multimedia) consumes a lot of energy.
• If one battery fails, the second one can temporarily support operation.

Batteries are connected sequentially (plus one to the minus of the other) so that the total voltage is 24V.