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What Does a Heavy-Duty Diesel Mechanic Do?
Dive into the world of heavy-duty diesel mechanic training. Find out more about this in-demand career path and about diesel training at UTI!
There are many different heavy-duty and diesel vehicles on the road today. In the United States, truck classification systems are used to help signify what large vehicles are built to do.
Those working in the automotive and diesel industries are familiar with these systems. Instead of simply seeing a truck driving down the street, they know how to sort these vehicles into their proper classes and designations.
There are many reasons why these classification systems are important. If you operate these types of vehicles or plan to work on them in a career as a diesel technician, having this knowledge is essential.
Keep reading to find out more about the systems, along with how different vehicles are classified.
Gross Vehicle Weight Rating
Vehicles in the U.S. are classified by gross vehicle weight rating (GVWR) on a scale of 1 through 9, with 9 being the largest possible GVWR.
Truck classification looks at the GVWR, which is the maximum truck weight plus the amount it can carry fully loaded. This includes:
- Passengers.
- Fuel.
- Products/cargo.
- Accessories like the trailer tongue.
These classifications are important for safety and commercial designation when vehicles are registered. They also can help determine whether a truck should stop at a weigh station, how long a truck is able to operate and what kind of permits are required for someone to drive it.
Certain signs and permits might need to be identified when hauling oversize or overweight equipment. The Department of Transportation (DOT) also sets number regulations. If a vehicle weighs more than 10,000 pounds, there must be a DOT number on both sides.
Knowing the correct truck classification can also help technicians prepare to perform maintenance on a vehicle. A shop might need to set aside a certain amount of space and prepare the work area depending on which class the vehicle falls under.
Drivers need specific licenses to operate vehicles, including a commercial driver’s license (CDL). CDLs are divided into classes A, B and C. One factor that determines which license is required could be the GVWR, while another could be whether the vehicle is designed or used to carry more than 10 passengers including the driver.
Weight Limits for Truck Classifications
When it comes to the weight limits for truck classifications, these are numbers that vary per state. The Department of Transportation is a great resource for owners and operators of commercial trucks to utilize for seeking out weight limits of a particular state.
States have standards for these max weight levels depending on the number of axles a truck has. These standards are in place to help ensure that drivers remain safe on the road and keeps the roads free from damage due to overburdened vehicles.
How Trucks are Classified into Different Classes
Trucks are divided into different classes based on their GVWR. Simply put, a GVWR is the maximum amount of weight a vehicle can safely handle, including payload capacity, which is passengers and cargo. Most vehicles feature their GVWR on a safety label located on the driver’s side doorjamb.
Truck Classifications
The categories for classifying vehicles and trucks range from Class 1 to Class 9:
Classes 1-3: Light-duty
The first three classes encompass non-commercial vehicles. These can include SUVs, minivans and pickup trucks. These are considered light-duty vehicles.
Classes 4-6: Medium-duty
Medium trucks fall into this set, including some full-size trucks that are used non-commercially. Most of the vehicles in these classes are used commercially, though:
- Class 4: The GVWR for this class is between 14,001 and 16,000 pounds. The Ford F-450 Super Duty® truck falls into this range, along with box trucks, walk-in trucks and city delivery trucks.
- Class 5: Trucks between 16,001 and 19,500 pounds fall into this class. A few vehicles are used non-commercially in this class, but primarily this class includes bucket trucks and larger delivery and walk-in trucks.
- Class 6: What is a Class 6 truck? Medium-duty commercial trucks fall into this class, which covers between 19,501 and 26,000 pounds. School buses are included in this class, as well as beverage and single-axle trucks. This is also the class where the need for a CDL often starts.
Classes 7-8: Heavy-duty
Big rigs and other commercial, heavy-duty vehicles are classified starting in this section.
- Class 7: What is a Class 7 truck? GVWRs range from 26,001 to 33,000 pounds. Most of these vehicles may have three or more axles. Anything from city transit buses to street sweepers and smaller furniture trucks can fall into this category as well.
- Class 8: What is a Class 8 truck? Big rigs that have GVWRs over 33,000 pounds fall into this category and can sometimes be referred to as “severe duty” instead of heavy duty. Cement and dump trucks are present, along with big rigs from manufacturers like Peterbilt and Freightliner.
Class 9: Super-heavy/Special
While most semitrucks and heavy-duty vehicles are in Class 8, it’s possible for the maximum limit to be set on a case-by-case basis. This is done using the Federal Bridge Gross Weight formula.
- Class 9: This class includes super-heavy/special-duty trucks, like a five-axle single-trailer truck. It includes all five-axle vehicles consisting of two units, one of which is a tractor or straight truck power unit.
This helps big rigs that are longer and heavier navigate interstate highways. States also allow different exceptions depending on what the Federal Bridge Gross Weight formula determines.
Typical Uses of Truck Classes
Now that you know the classes for categorizing trucks and vehicles, you’re probably wondering what some of the most common uses are.
Classes 1-3: Common Uses
Truck classes 1-3 are known as light-duty vehicles or work trucks that have lower weight ranges, but they’re still used for a variety of tasks.
Class 1 encompasses compact pickups and utility vehicles that are often used for small repair businesses and other tasks. Class 2 trucks are defined as full-size pickups that are commonly used for moderately heavy loads, like what you see in landscaping or construction. Class 3 is one step above and often referred to as heavy-duty pickups that feature increased towing and carrying capacity, which makes them handy for transporting materials or trailers.
Classes 4-6: Common Uses
Classes 4-6 are considered medium-duty trucks. Often, these trucks are used in commercial applications. You might see them being used in construction, moving services, delivery or even as emergency response vehicles. Class 6 trucks may even feature specialized frames or bodies to accommodate the industries they’re being used for.
Classes 7-8: Common Uses
Heavy-duty trucks in classes 7 and 8 are what those in the industry seek for carrying a large amount of weight.
Think delivery driving, waste management and utility services, along with freights that help move along various goods around the country.
Class 9: Super-Heavy/Special Common Uses
Most vehicles fall into the first eight categories, but different vehicles may have different weight maximums that push them into Class 9. Some examples could be big rigs or trucks classified as heavy-duty construction equipment that are used for mining or heavy hauling jobs.
Truck Classification FAQs
What are the weight limits for each truck class?
- Class 1: < 6,000 pounds.
- Class 2: 6,001-10,000 pounds.
- Class 3: 10,001-14,000 pounds.
- Class 4: 14,001-16,000 pounds.
- Class 5: 16,001-19,500 pounds.
- Class 6: 19,501-26,000 pounds.
- Class 7: 26,001-33,000 pounds.
- Class 8: >33,001 pounds.
- Class 9: determined using the Federal Bridge Gross Weight formula.
Where can I find a truck weight class chart?
The U.S Department of Energy features a Vehicle Weight Classes & Categories chart on its website, along with several other resources. The DOT is also useful for identifying different truck weight limits depending on the state.
How are trucks classified into different classes?
Trucks are divided into different classes based on their GVWR, or gross vehicle weight rating, which is the amount of weight they can safely handle.
Train on Diesel Technology at UTI
There are many different classifications for vehicles and trucks. One thing that remains true is the importance of keeping these vehicles operating well.
These powerful machines rely on trained diesel technicians to keep them operational so they can perform important tasks that impact our daily lives. You can enroll in the Diesel Technology program offered at UTI and learn how to diagnose and repair problems on a range of large trucks.
In as little as 45 weeks7 you can graduate with the hands-on experience and knowledge it takes to become an entry-level technician in the industry.1
Interested in finding out more? Request more information today!
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