Semi Trucks Trailers Parts

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Semi Trucks Trailers Parts and engine parts


United States

Semi Truck Parts

Currently, the main primary source of power for semi trucks is the diesel engine. Some fleets have opted for natural gas sources such as LNG, but it does not have the same level of infrastructure built to accommodate fueling and repairs. Regardless of engine type, all engines built in today’s time are computer controlled.

Note: indicates product sheets updated in the last 7 days.

Distance variations

There are specific names and terms given to distances between certain parts on a semi-truck. Common term and phrases include:

  • Wheelbase – The distance between the center of the steer and drive axles
  • Trailer-length – the overall semi-trailer length. This is usually 48FT or 53FT.
  • Overall wheelbase – The wheel base between the centerline of the steer axle and the rearmost axle of the trailer
  • Landing gear clearance – The landing gear clearance is the center point to the nearest point of interference.
  • Kingpin setting – the front of semi-trailer to the center of kingpin on semi-trailer.

Electrical Systems

The truck’s electrical systems are comprised of its batteries, alternator, and starter that must be in accordance with the engines requirements. Without the electrical systems certain features of the truck would not work including the starter, lighting, windshield wiper motors, computer system operation, and the cabin amenities such as a power inverter.


Majority of heavy trucks have a push or pull clutch. Some trucks have centrifugal or wet clutches. Trucks with higher torque ratings have a two-plate clutch. The purpose of a two-plate clutch is to increase the friction area and transmit it to the transmission without any slippage. Automated manual transmission equipped trucks have clutches that are managed electronically.

Torque Converters

Torque converters are found in fully-automatic transmissions such as the ones made by Alison. It is like a clutch for manual trucks but works in a different way. Torque converters are classified as fluid couplings because they use hydrodynamics.


Heavy-duty truck transmissions are manual, automated manual, or automatic. Various components of the transmission must provide superior performance for hundreds of thousands of miles. These components of the transmission include the gears, shafts, forks, and bearings.

Manual transmissions have two or three countershafts that transmit engine torque from the input to output shaft. The countershafts distribute torque two or three directions, and this results in reduced strain on individual gears.

Automated manual transmissions do not have a clutch pedal because the clutch is actuated automatically. The I-SHIFT transmission by Volvo is an example of an automated manual transmission.

Drive Shafts

The driveshaft is a tube with flanges or end yoke that is attached to the output shaft of the transmission and it helps with maneuverability of the drive axles. Parts of the drive shaft are interconnected with each other and with the transmission with universal joints which allow torque to transmit



Axles give the suspension, wheels, and steering parts a place to be mounted. The drive axles have differential gear shafts which help truckers in the snow prevent their truck from sliding. The front axle is called the steer axle. The rear-two axles are called the drive axles.

Steering Components

Two main types of steering systems are found in heavy trucks. They are manual and power steering assist systems. Manual steering systems have worm roller or recirculating ball gears. Power steering assist use a hydraulic pump. Rack and pinion steering are found in newer trucks that provide better control.

Air Brakes

Air brakes is the most common type of brake system on a heavy truck. Air brakes use a complicated network of pneumatic lines, valves and cylinder that maintain the transfer of compressed air to the brakes.

Chassis Frame

The chassis frame includes the rails and crossmembers of the truck and the strength of these components impacts the truck’s durability to carry heavy loads. Frame designs vary by manufacturer.

Fifth Wheel

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

Heating, Ventilation, Air Conditioning (HVAC)


HVAC systems are responsible for climate control of the tractor unit. Some HVAC systems are coupled with auxiliary systems that help balance the in-cabin temperature with engine temperature and engine shutdown features to prevent over-heating. Anti-idling laws are creating an increased need for sophisticated HVAC systems. For example, the development of parking heaters has aided in preventing trucks from idling for extended periods of time.



A commercial truck is an indispensable business asset, one that is most valuable when it’s operational, on the road or at a job site. Downtime, when the truck isn’t running, costs money, both in terms of lost productivity and the outlay for repairs to make the truck functional again. The best ways to reduce downtime and lost revenue are with preventive maintenance and timely repairs, and using quality, affordable parts when performing vehicle service, like the kind you’ll find here on our digital shelves. We have all the products you need to keep your truck running well and performing reliably, with parts and supplies for everything from oil changes to major overhauls. Our selection includes brake, suspension, engine, fuel delivery, exhaust, transmission, driveline parts, and more, and with a phone call or a few keystrokes they can be delivered right to your door.

Regular preventive maintenance and vehicle inspections can help avoid costly breakdowns and major repairs. Maintenance and inspection tasks and their frequency will vary according to the type of truck and how it is used and may be scheduled according to mileage, time, or engine hour intervals, and service may also be required in response to problems reported by the driver. We recommend that you follow the service checklist and schedule of tasks and inspections that are appropriate for your truck and the way you use it and see us for everything needed to get the job done right. We have conventional, synthetic, and synthetic blend motor oils in all popular grades that are specially developed to meet the demands of gasoline and diesel truck engines used in severe operating conditions, as well as transmission fluid, transfer case lubricant, gear oil, coolant, and brake fluid for topping off and changes, high temperature grease for bearings and lubricating suspension, steering, and driveline fittings, and many other types of cleaners, degreasers, additives and multi-purpose lubricants.

Of course, in addition to our full complement of consumables, we have the parts commonly needed for maintenance tasks including engine air filters, cabin air filters, oil filters, gasoline and diesel engine fuel filters and diesel engine fuel/water separator filters, automatic transmission filters, and spark plugs. Here you’ll also find replacements for parts that are typically found to be worn or defective during vehicle inspections, like wiper blades, bulbs, accessory drive belts, cooling system hoses, ignition wires, and brake pads & shoes, as well as gaskets and seals for repairing fluid leaks. However, since many other defects can be found during a vehicle inspection, and because even with well implemented and designed preventive maintenance plans parts can still fail, we offer a large selection of parts for all types of medium and heavy-duty trucks and for every truck system, so you can make repairs and quickly have the truck back on the job. The lifespan in terms of miles is exponentially greater for a commercial truck than for the average family car. Accordingly, parts must be made to a level of quality that can stand up to this type of severe usage, and they’re the only kind of parts we stock on our virtual shelves.

The truck’s batteries should be maintained and regularly checked to prevent a no-start. When replacement is required we have batteries with the cranking amps needed to start large truck engines, as well as battery cables, starters, alternators, voltage regulators, solenoids, relays and everything else to keep your starting and charging system in good repair. We also have what you need to affordably repair many other electrical system problems including remanufactured instrument clusters; wiper motors, switches, and washer pumps; headlight, turn signal, brake light, and dimmer switches; power window motors and switches; power door lock actuators and switches; and many other replacement electrical components. And you’ll be warm inside your truck on frigid winter days and cool and comfortable in the cab when the outside is baking in the sweltering summer sun when you service your rig with our A/C & heating parts. We have compressors and clutches, blower motors, heater cores, evaporators, condensers and condenser fans, receiver driers and accumulators, and expansion valves and orifice tubes.

If brake inspection revealed that more work was needed than just pads and/or shoes, we have brake rotors and brake drums plus all the parts necessary to service both hydraulic brake and air brake systems, mechanical parking brakes, brake boosters, anti-lock brake systems, and more. No matter what type of suspension system is on your truck, conventional mechanical springs or air suspension, we have the replacement parts to restore or upgrade handling, ride quality and load carrying capability, including coil, leaf and air springs, helper springs, shock absorbers, bushings, ball joints, and sway bars. For steering system service, we offer complete steering gear boxes and steering gear rebuild kits; steering linkage including the pitman arm, idler arm, center link, drag link, tie rod ends and adjusting sleeves; steering knuckles and kingpin sets; power steering components including pumps, pulleys, reservoirs, coolers, and lines and hoses; and steering dampers and stabilizers.

Whether you want to repair or replace the gasoline or diesel engine in your truck, we have the parts to meet your needs, from complete engine assemblies to motor mounts. Here you’ll find remanufactured long blocks and short blocks, turbochargers and intercoolers, oil pumps and oil coolers, timing chains & sprockets and timing gears, oil pans and valve covers, and much more. To keep your gasoline engine fed we have mechanical and electric fuel pumps, pressure regulators, injectors, throttle bodies and carburetors, as well as injection pumps, injectors, and glow plugs for their diesel counterparts. If you’re not getting adequate spark we have ignition components including coils, modules, and distributors to restore complete combustion. And if you’re exhaust is getting loud or you’ve detected dangerous exhaust leaks during vehicle inspection, we have the parts to restore quietness and system integrity, from the manifold to the tailpipe and the muffler, exhaust pipes, and clamps, hangers, and gaskets in between.

Keeping your engine within it’s designed operating temperature range will provide the best performance, fuel mileage, and durability, and we have the parts required to make it happen including radiators, fans, water pumps and thermostats, expansion and overflow tanks, and temperature sensors and switches. Plus, we have an extensive collection of parts to keep your truck running well and emissions compliant, featuring oxygen sensors, catalytic converters, diesel emission fluid tanks and pumps, EGR valves and coolers, PCV valves and secondary air injection pumps. Be it automatic or manual transmission equipped, we have the transmission and driveline parts to ensure you get all your truck’s engine power to the wheels. Our selection includes automatic transmission assemblies, torque converters and internal parts; clutch kits, flywheels, and clutch linkage; transfer case motors; driveshaft assemblies, yokes, center supports, and U-joints; axles, bearings and differential components; and wheel hubs, bearings, and seals.