What Are The Parts Of A Tractor Trailer?

Parts of a Semi Truck Diagram

The diesel engine is the most common source of power for semi trucks; some fleets have opted for natural gas sources such as LNG, but it lacks the same infrastructure for fueling and repairs. Regardless of engine type, all engines built today are computer controlled.

Distance variations

The landing gear clearance is measured from the center of the semi-trailer to the closest point of interference, and the kingpin setting is measured from the front of the semi-trailer to the center of the kingpin on the trailer.

Electrical Systems

Certain aspects of the truck would not function without the electrical systems, including the starter, lighting, windshield wiper motors, computer system operation, and cabin amenities like an inverter.


Trucks with higher torque ratings have a two-plate clutch, and trucks with automated manual transmissions have clutches that are managed electronically. Some trucks have centrifugal or wet clutches to increase the friction area and transmit it to the transmission.

Torque Converters

Torque converters are found in fully automatic transmissions like Alison’s, and work similarly to a clutch for manual trucks, but in a different way. Torque converters are classified as fluid couplings because they work with hydrodynamics.


Manual transmissions have two or three countershafts that transmit engine torque from the input to output shafts, while automated manual transmissions do not have a clutch pedal because the clutch is actuated automatically.

Drive Shafts

The driveshaft is a tube with flanges or an end yoke attached to the transmission’s output shaft that aids maneuverability. Parts of the drive shaft are interconnected with each other and with the transmission via universal joints that allow torque to be transmitted.


The front axle is known as the steer axle, and the rear-two axles are known as the drive axles. The front axle is known as the steer axle, and the rear-two axles are known as the drive axles. Drive axles have differential gear shafts that help truckers in the snow prevent their truck from sliding.

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Steering Components

In heavy trucks, there are two types of steering systems: manual steering systems with worm roller or recirculating ball gears, and power steering assist with a hydraulic pump. Newer trucks have rack and pinion steering systems, which provide better control.

Air Brakes

The most common type of brake system on a heavy truck is air brakes, which use a complicated network of pneumatic lines, valves, and cylinders to keep compressed air flowing to the brakes.

Chassis Frame

The strength of these components, such as the rails and crossmembers, determines the truck’s strength. Frame designs differ from manufacturer to manufacturer and can be quite different.

Fifth Wheel

The fifth wheel is the part of a semi-tractor that connects to the trailer’s kingpin. Fifth wheels can be positioned or slide back and forth to allow proper trailer weight distribution on the tractor’s drive axles, and the type of connection formed between the fifth wheel and the kingpin allows the truck to articulate when turning.

Heating, Ventilation, Air Conditioning (HVAC)

Anti-idling laws, it has been claimed, are increasing the need for sophisticated HVAC systems. Some HVAC systems are coupled with auxiliary systems that help balance the in-cabin temperature with engine temperature and engine shutdown features to prevent overheating.

What are the parts of a tractor trailer called?

The legend for the truck’s labeled parts is as follows:

  • Tractor unit.
  • Semi-trailer (detachable)
  • Engine compartment.
  • Cabin.
  • Sleeper (not present in all trucks)
  • Air dam (not present in all trucks)
  • Fuel tanks.

What are the parts on a semi truck?

The legend for the truck’s labeled parts is as follows:

  • Air dam.
  • Fuel tanks.
  • Fifth-wheel coupling.
  • Tractor unit.
  • Semi-trailer (detachable)
  • Engine compartment.
  • Cabin.
  • Sleeper (not present in all trucks)
  • Air dam.
  • Fifth-wheel coupling
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What are the parts of a semi-trailer called?

A tractor unit, a detachable front-axle assembly known as a dolly, or the tail of another trailer support a large portion of a semi-trailer’s weight, while its own wheels only support the semi-trailer’s rear.

What is the back part of an 18 wheeler called?

Aerodynamic panel skirts, side panels, or side skirts are the panels under the truck’s body, while rear tail fairings, trailer tails, or boat tails are the panels that hang off the back.

What are 18 wheelers called?

Although not all semi-tractor-trailers have 18 wheels, those that do are referred to as 18-wheelers, why is it called a semi truck, and what really distinguishes semis from other trucks?

Why are trucks 53 feet long?

The typical North American grocer’s pallet is 48 inches long by 40 inches wide, and as trailers grew in size, they did so in multiples of 4 feet until the regulations were changed, and the industry adopted the 53-foot trailer, which has room for 13 rows of pallets plus an extra foot to allow for the door to close.

Why is it called a semi truck?

The answer is simple: semi-truck or semi is short for semi-trailer truck, and the u201csemiu201d part of the title refers to what the tractor is pulling behind it, not the size of the big rig.

What is truck head called?

Tractor Head is one of the truck types designed to tow a trailer; it is usually referred to as “Tractor Head,” but some countries refer to it as “Prime Mover,” and in Japan, we refer to it as “Trailer Head” because we associate “tractor” with agricultural tractors.

What do you call the front of a truck?

A pickup truck’s front end consists of a hood (also known as an engine cover or a bonnet in the UK), front quarter panels or fenders, grill, headlights, parking lights, turn signal lights, and a front bumper attached to the frame or chassis.

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What are the legs of a semi-trailer called?

The landing gear is a pair of retractable “legs” attached to the underside of a trailer on either side of the “fifth wheel,” a horseshoe-shaped component on the back of a cab that locks onto the king pin, a vertical steel pin jutting from the bottom of the semi-trailer’s front.

What is a 18 wheel truck?

An 18-wheeler is a combination of a semi truck/tractor and a trailer, with a total of 18 rims and wheels on each rim, 10 rims/tires on the truck/trailer and 8 rims/tires on the trailer.

What is the back of a trailer called?

Crossmember Spacing: The distance between crossmember centers. Crossmember, Rear: The transverse member at the extreme rear of a trailer to which the bumper is normally mounted and on which the stop, tail, and turn lights are often installed.

What are 16 wheelers called?

The Anatomy of a Tractor Trailer As the name implies, 16 wheeler trucks have 16 wheels rather than 18. Tractor trailer engines can be up to six times the size and weight of a car engine.

How many gears does a 18 wheeler have?

Most 18-wheelers today have ten forward and two reverse drive gears, but this varies widely depending on the truck’s manufacturer; semi-tractors can have as few as nine gears and as many as eighteen.

What is the box on the back of a truck called?

The back of a standard pickup truck is known as the cargo bed, but it is more commonly referred to as just a bed. It is a section of the truck that is dedicated to storage and is separated from the cab of the vehicle. This part of the truck provides storage space to keep the inside of the truck free of tools and clutter.

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