Which Axle Drives a Semi-Truck? Key Insights and Maintenance Tips

25 Aug.,2025

 

Which Axle Drives a Semi-Truck? Key Insights and Maintenance Tips

Ever wondered what keeps those massive semi-trucks moving smoothly on the highways? The answer lies in their axles. Semi-trucks, also known as tractor-trailers or big rigs, are the backbone of long-haul transportation, and their axles play a crucial role in supporting the vehicle's weight.

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Let’s identify how many axles does a semi truck have, common issues, and maintenance tips to keep these giants rolling.

Which Axle is the Primary Drive Axle on a Semi-Truck?

It is typically one of the rear tandem axles. These axles are pivotal in transmitting the engine's power to the wheels, enabling the truck to move forward or backward. They are connected to the engine via the transmission and differential, which manage the distribution of power efficiently.

Drive axles come equipped with differentials that allow each wheel to rotate at different speeds, a crucial feature when making turns. This prevents tire wear and ensures smoother handling. In modern semi-trucks, drive axles may incorporate advanced technology such as torque vectoring. Torque vectoring dynamically adjusts the amount of power sent to each wheel, optimizing traction and performance under various driving conditions.

Understanding the different types of drive axles is important. For instance, some trucks use a single drive axle, while others may have multiple drive axles to handle heavier loads. The configuration can vary depending on the truck's design and the demands of the transport job.

For a comprehensive overview of the role of drive axles in heavy-duty commercial vehicles, check out the video below ????????

Common Issues Affecting Semi-Truck Axles

Knowing the role of the drive axle is essential, but it's equally important to be aware of the common issues that can affect these critical components, such as:

1. Wear and Tear:

Semi-truck axles endure significant wear due to heavy loads and long distances. Regular inspections are necessary to identify and address wear-related issues. Common wear points include bearings, seals, and axle shafts, which require constant monitoring.

2. Axle Misalignment:

Misalignment can result in uneven tire wear, reduced fuel efficiency, and poor handling. Regular alignment checks can prevent these issues. Causes include potholes, heavy impacts, and general wear, making professional alignment services essential.

3. Brake Problems:

Axles are integral to the braking system; any issues can compromise braking efficiency. Regular maintenance of brake components attached to axles is crucial. This includes checking brake pads, rotors, and ensuring proper hydraulic or air pressure in the braking system.

4. Lubrication Issues:

Proper lubrication of axle components prevents overheating and excessive wear. Regular lubrication checks and maintenance are essential for axle longevity, including inspecting for leaks and using the appropriate type of grease or oil.

5. Load Distribution:

Incorrect load distribution can lead to axle damage and reduced vehicle stability. Ensuring proper loading practices can prevent these problems. Overloading or uneven loading can stress axles and lead to premature failure, emphasizing the need for correct loading guidelines and tools.

Essential Maintenance Tips for Semi-Truck Axles

To keep your semi-truck running smoothly and safely, it's crucial to maintain its axles regularly. Proper maintenance not only extends the lifespan of your truck but also ensures efficiency and safety on the road. Here are some essential tips to help you maintain your semi-truck axles in top condition.

- Proper Lubrication.

Use the recommended lubricants and follow the manufacturer’s maintenance schedule. Regularly check and replenish lubrication to ensure smooth operation. Pay attention to changing lubricants seasonally if required for varying temperatures, maintaining consistent axle performance.

- Alignment Checks.

Conduct alignment checks to prevent misalignment-related issues. Proper alignment enhances handling, tire life, and fuel efficiency. Use professional alignment services to ensure precision, addressing any misalignment promptly.

- Correct Load Distribution.

Ensure even load distribution to prevent axle strain and damage. Follow loading guidelines and use load distribution tools if necessary. Train loading personnel on the importance of proper weight distribution, minimizing the risk of axle damage.

- Brake System Maintenance.

Regularly inspect and maintain brake components connected to axles. Ensure brakes are in good condition to maintain safety and performance. Check for wear on brake pads, ensure proper functioning of brake chambers, and maintain air lines to ensure reliable braking.

- Regular Inspections.

Schedule routine inspections to check for wear, alignment, and proper lubrication. Early detection of issues can prevent costly repairs and breakdowns. Use a checklist to ensure all critical components are inspected, ensuring thorough and effective maintenance.

Consistent and thorough inspections are key to keeping your semi-truck in peak condition. For a detailed guide on performing effective inspections, check out the video below ????????

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By following these maintenance tips, you can enhance the longevity and performance of your semi-truck axles. Regular attention to these components ensures smoother, safer journeys on the road. 

Understanding the axles on semi-trucks, functions, and the common issues they face is crucial for maintaining these vehicles' safety and efficiency. Regular maintenance and proper care of axles can significantly extend their lifespan and enhance the overall performance of semi-trucks.

Heavy Haul Trucking: How Does Freight Weight Impact Trailer Type?

  • How heavy haul freight weight impacts trailer selection
  • Trailer type breakdown by weight

Heavy haul trucking can be exciting. The trucks are big, the trailers are long and the freight can get reaaaal heavy.

But there's also a ton to learn in the world of heavy haul, and even those who’ve worked in this industry for years uncover something new every now and then. It can be overwhelming for newcomers to heavy freight as they try to get a handle on all the intricacies.  

Here at ATS, we’ve been a staple of the U.S. trucking industry since our early days in . During this time we’ve been helping customers transport all kinds of freight at all kinds of weight, including a significant volume of heavy haul trucking.

As such, we understand how the amount a shipment weighs correlates to the type of trailer it’s transported on, and — by the end of this article — you’ll understand this too. 

How Heavy Haul Freight Weight Impacts Trailer Selection

Before we get into the nitty-gritty of this discussion its important that you understand a couple of general rules when it comes to trailers: 

Not All Trailers Are Created Equal 

By this, I don’t mean that some trailers are of higher quality than others — although some are. Instead, I mean that the amount of weight each trailer can support varies marginally from one manufacturer to another. 

Some manufacturers make their trailers a bit wider or from stronger materials so that they can handle more concentrated weight. Others manufacture trailers that have more well-space to disperse extra weight. Some others use heavier materials like steel in their construction which limits their weight capacity slightly. 

Although these discrepancies between one manufacturer and another mean little when transporting smaller quantities of freight, they can make a difference as load weight and capacity requirements increase.

With this in mind, it’s important you understand that — although the capacity thresholds listed below are great general rules-of-thumb — the exact maximum weight capacity of each trailer will vary based on the manufacturer, make and model. 

State Regulations Will Also Impact Maximum Weight/Axle Limits

Each state has its own mandated guidelines for the maximum amount of weight that’s legally allowed to accompany each tractor/trailer set-up. 

Although — in the interest of safety — the Federal Government also stipulates the legal weight limits, procedures and routes of heavy haul freight, these mandates can be adjusted state-by-state. 

As such, it’s important you understand that all of the weight/trailer type capacities we provide in this article are subject to change based on where each load is being transported. 

Partnering with a seasoned transportation provider with a demonstrated history of successfully routing heavy haul freight will help you navigate these — often complex — waters.   

Trailer Type Breakdown by Freight Weight

Before diving into our breakdown, it's important to note that the ranges listed below are based on what each trailer can haul without consideration of weight limit restrictions.

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Again, because legal weight limits vary by location, it is critical that you investigate what restrictions are in place at every stage of your route. 

With that little disclaimer out of the way, let's get into it! 

  • 55,000 lbs. or less
  • 55,001 - 65,000 lbs.
  • 65,001 - 84,000 lbs.
  • 84,001 - 94,000 lbs.
  • 94,001 - 107,000 lbs.
  • 107,001 - 118,000 lbs.
  • 118,001 - 125,000 lbs.
  • 125,001 - 135,000 lbs.
  • 135,001 - 150,000 lbs.
  • 150,001 - 225,000 lbs.
  • 225,001 - 360,000 lbs.
  • 400,000+ lbs. 

55,000 Pounds or Less

The vast majority of freight occupying the roads today weighs less than the 55,000-pound capacity limitations of a five-axle setup. 

As such, most shippers use the following two-axle trailer types to haul freight weighing 55,000 pounds or less:

  • Double drop
  • Dry van
  • Flatbed
  • Step-deck
  • Reefer
  • Removable gooseneck (RGN)

For companies that frequently transport pallet-based, boxed or consumer goods, building materials ,and perishable freight, these five-axle combos (3-axle truck + 2-axle trailer) are more than sufficient. 

55,001 - 65,000 Pounds

As soon as a shipment hits the 55,000-65,000 pound range, adding a third axle will be necessary due to the weight-bearing limitations of a two-axle trailer.

These tri-axle trailers look very similar to their bi-axel counterparts and come in several equipment types, including:

  • 3-axle flatbeds
  • 3-axle step-decks
  • 3-axle removable goosenecks (RGNs)

In total, these truck/trailer combos boast six axles (3-axle truck + 3-axle trailer) and do an excellent job transporting a variety of heavier freight. 

65,001 - 84,000 Pounds

When total freight weight falls within the range of 65,001-84,000 pounds, it's time to look at specialized “heavy haul trucks."

These quad-axle trucks possess a single axle in front (called a “steer axle”) and three axles in the back (known as the “drive axles”). 

All four of these axles are necessary for supporting massive amounts of weight from point A to B. 

Like the previous weight range, a three-axle trailer is used for freight weighing up to the 84,000-pound threshold. 

You’ll need seven total axles (4-axle truck + 3-axle trailer) to transport any large machinery, generators or other heavy freight that falls within this weight range. 

84,001 - 94,000 Pounds (8 Axles)

As we continue past 84,000 pounds, freight will require an 8-axle combination for safe transport. There are a few different ways trailers can be safely configured to achieve this. 

Method 1: A carrier can use a “closed quad," a trailer with four axles located at the rear end of their decks. These “closed quad” trailers, coupled with the four-axle truck, provide the necessary eight total axles.

Method 2: Also known as a “three plus one” configuration, carriers can utilize a regular three-axle trailer accompanied by a one-axle “stinger." This combination of trailers, plus a four-axle truck, also comes to eight total axles.

Depending on state regulations, the amount of total weight an eight-axle setup (and all subsequent configurations) can haul may change. Always check the regulations in every state through which your heavy haul freight will travel.

94,001 - 107,000 Pounds (9 Axles)

Once a shipment’s weight goes above 94,000 pounds, nine total axles are needed to haul that load.

There are a variety of configurations to achieve this, many of which incorporate combinations of "jeep" and "booster/stinger" dollies.

What Is a Jeep Dolly? (Jeeps)

A jeep dolly is a shorter trailer that includes a sliding fifth wheel, kingpin, and a system of suspension. These 1-3 axle units are used as the intermediary between the main trailer and the tractor. 

What Is a Booster/Stinger Dolly?

"Booster" or "stinger" dollies, also called "tail-waggers," are  are 1-3-axle rear units attached immediately behind the main trailer. 

Booster/stinger dollies are very common solutions in heavy haul transportation.

9-Axle Combinations

Here are some component combinations that make transporting large construction equipment within the 94,001 - 107,000 pound range  possible:

  • 4-axle truck + 5-axle trailer
  • 3-axle truck + 2-axle jeep dolly + 2-axle trailer + 2-axle booster/stinger
  • 3-axle truck + 2-axle jeep dolly + 3-axle trailer + 1-axle booster/stinger

107,001 - 118,000 Pounds (10 Axles)

This is where things start to get complex. At this point, you’re transporting very large pieces of freight, which requires some expert logistical oversight — and 10 total axles, to boot.

Although the exact combination of components will vary depending on your shipment’s requirements (which is why finding an experienced provider is key), here are a few ways 10-axle combinations can be formatted:

  • 4-axle truck + 3-axle jeep dolly + 3-axle trailer
  • 4-axle truck + 2-axle jeep dolly + 3-axle trailer + 1-axle booster/stinger
  • 4-axle truck + 2-axle jeep dolly + 2-axle trailer + 2-axle booster/stinger

118,001 - 125,000 Pounds (11 Axles)

Here are some jeep, trailer, and stinger combinations frequently used to transport freight falling within the 118,001 - 125,000 pound range on 11 total axles:

  • 4-axle truck + 3-axle jeep dolly + 4-axle trailer
  • 4-axle truck + 2-axle jeep dolly + 3-axle trailer + 2-axle booster/stinger
  • 4-axle truck + 3-axle jeep dolly + 3-axle trailer + 1-axle booster/stinger
  • 4-axle truck + 2-axle jeep dolly + 4-axle trailer + 1-axle booster/stinger

125,001 - 135,000 Pounds (12 Axles)

12 total axles are required as soon as your load meets or exceeds 125,000 pounds. Like the previous few weight classes, this is done using various combinations of trailers, jeeps, and stinger components. 

Here are a few ways a 12-axle combination can come together:

  • 4-axle truck + 2-axle jeep + 4-axle trailer + 2-axle booster/stinger
  • 4-axle truck + 3-axle jeep + 3-axle trailer + 2-axle booster/stinger

135,001 - 150,000 Pounds (13 Axles)

Any time you need to move freight that exceeds 135,000 pounds in weight, at least 13 axles will need to be involved. 

Again, there are many combinations for how a carrier can achieve the 13 axles necessary for these heavy haul shipments. Here's just a pair:

  • 4-axle truck + 3-axle jeep + 3-axle trailer + 3-axle booster/stinger
  • 4-axle truck + 3-axle jeep + 4-axle trailer + 2-axle booster/stinger

150,001 - 225,000 Pounds (19 Axles)

If you noticed a big jump in axles here, that's no mistake: Once a shipment exceeds 150,000 pounds, they usually require at least 19 total axles.

These 19-axle setups are often used to haul huge tanks (vessels), boilers, and generators, among other oversized and over-heavy freight.

They also look a bit different from trailers used to haul lighter freight. They feature a 32-56 foot deck coupled with a 4-axle truck to achieve the 19 total axle requirement.

225,001 - 360,000 Pounds (Up to 24 Axles)

The next step up when transporting heavy haul freight from 225,000 (20 axles) up to 360,000 pounds (24 axles) is to use as a “dual-lane” trailer.

These highly specialized trailers are used to haul massive boilers, generators, tanks, oil and gas skids, and more.

As their name suggests, dual-lane trailers transport freight along interstate highways using both lanes. Because of the traffic disruptions these shipments cause, they can take 2-6 months of planning.

Generally speaking, these trailers are only able to complete about 6-8 hauls in a calendar year. This because of the slow-moving nature of these shipments, which generally take upwards of a month to complete a single round-trip. 

Due to maneuverability restrictions, dual-lane trailers often require a tractor on both ends to assist with steering, depending on the length, height and weight of the freight in question. 

400,000+ Pounds (Line Trailers)

When freight hits the 400,000+ range — nearly half a million pounds! — the only type of trailer that can handle the extraordinary weight is the modular line trailer. 

Line trailers are specialized hauling solutions that can add or subtract axles as needed to adequately distribute a shipment’s weight. They can be adjusted up to 36 axles and are the go-to solution for freight that’s difficult to disassemble. 

When the weight is this high, so are the stakes. Transportation of freight at this weight threshold is a truly specialized service, one that will need to be sought out well in advance.

We recommend seeking out transportation providers that consider line trailer transportation a key area of expertise or a primary service offered. 

How to Make Your Next Shipment a Success

Now that you have a better understanding of how freight weight and trailer type operate in relation to one another, download our Trailer Fit Equation Guide, which outlines some general rules for calculating the load weight/number of axles needed. 

If you’re a shipper who needs to move a shipment that has a weight of 55,001+ pounds, you’ll need to plan for the logistical aspects of these heavy haul shipments. 

The best way to do so is to find a seasoned transportation partner with a demonstrated history of transporting these shipments correctly and safely. In the business of moving heavy haul shipments, nothing is more important than leveraging expertise. Finding the right partner will help you do this.  

These transportation providers will help you understand how your shipment’s route in relation to its specifications will impact your timelines. 

Contact us to discuss your requirements of Multi Axle Semi Trailer. Our experienced sales team can help you identify the options that best suit your needs.