The Ultimate Semi-Truck Maintenance Checklist; 2025 Guide

To have a successful trucking business, ensure you check and maintain your trucks and trailers regularly. 

Before any trips, check and maintain your semi-trucks, medium-duty trucks, semi-trailers, and heavy-duty trucks to ensure they are in good condition and up to their functionality. 

Regular maintenance is vital for keeping these vehicles running smoothly. Don't forget to inspect them thoroughly before hitting the road. 

This guide helps truck drivers, owners, and fleet managers find and solve performance problems with their semi-trucks. 

Let's dive right in.

Why You Need a Semi-Truck Maintenance Checklist 

Does your truck require significant maintenance to operate correctly? The answer is yes. Having a maintenance checklist for your heavy truck is essential. This helps you keep track of critical parts, spot any problems, and fix them.

The government has rules for truckers. These rules require them to check, fix, and care for their trucks. The purpose is to ensure that the trucks are safe to use.

According to the Code of Federal Regulation part 363.1, “Every motor carrier and intermodal equipment provider must systematically inspect, repair, and maintain, or cause to be systematically inspected, repaired, and maintained, all motor vehicles and intermodal equipment subject to its control.”

Here are the benefits of maintaining your big rig.

1. Timely maintenance is necessary to keep your truck's important parts running correctly and in optimum condition. Always perform regular checks and solve any engine and brake problems, among other issues, before your truck leaves for a trip.
2. Well-maintained trucks will always remain productive and help your fleet earn the trust of customers and employees. They will consistently deliver the goods on time without in-between trip breakdowns.
3. Doing maintenance early is preferable to waiting for a significant issue that requires expensive repairs. Identifying and addressing the problem early before it worsens will help increase your profit margin and reduce unnecessary losses.
4. Regular maintenance can make trucks last longer, keeping them running longer.
5. Keeping semi-trucks well-maintained can prevent accidents, protect employees and the public, and save the company from liabilities.

What to Include and Inspect in Your Semi-truck Maintenance Checklist

1. The Engine System

The engine is an integral part of a vehicle. Just like a human heart, if it fails to function as required, your semi-truck is dead without it. 

Therefore, you need to take care of the engine for smooth operation. Failure to do so will cause your vehicle to experience many issues that may cost you thousands of dollars.

Here is a list of the parts of an engine system to inspect and provide feedback on their state.

• Coolants
• Hoses
• Belts
• Radiators
• Engine oil
• Oil filters
• Driveshafts
• CV Joints
• Exhaust system
• Transmission mount

Indicators of a Defective Diesel Engine

Overheating. This can result from poor lubrication, clogged hoses, bent radiators, low coolant levels, and broken plugs. 

Note that overheating can lead to permanent engine failure. Always perform regular checks to ensure your engine is in good condition and functioning correctly.

Failure to start. This happens when you turn on your truck, and the engine fails to start. Sometimes, it can be a battery problem. Check on your vehicle's battery. 

Black smoke and a strange smell. Heavy black smoke and an unfamiliar smell emanating from your semi-truck engine are signals of a damaged engine that needs immediate attention.

Failure to shut down. You have turned off your semi-truck and removed the key, but the engine keeps running. This indicates that either a solenoid or the engine's carburetor has a problem.

Power loss. This serious faulty engine issue occurs when your truck is in transit. Either it will lose power entirely and shut down or suddenly stall out.

High diesel consumption. If your truck uses more fuel than usual for a certain distance, it may have engine issues that require repair. This could be causing the increased fuel consumption.

It is important to address these problems promptly to prevent further damage. Ignoring the issue could lead to more costly repairs in the future.

Banging, popping, backfiring, or hissing noises. A faulty engine will produce rough sounds when in operation. This indicates that it is time to see a professional mechanic before it gets out of hand.

Oil stains below your truck. This can result from an oil leak in your engine.

When the check engine light turns on. The engine light will turn on to notify you of a minor or severe problem in your engine’s internal system. These are signs that you should not ignore. Always call a licensed electrician for a diagnosis.

Note: Always watch for the signals, as mentioned above, of a faulty engine and reach out to an expert who will diagnose and identify your engine problem and provide suggestions on how to solve the problem.

2. Braking Systems

A braking system is an integral part of a truck that helps the driver brake and stop where necessary. Suppose the hydraulic or air brake is not functioning correctly. 

In that case, your vehicle may put the lives of your driver, other drivers, pedestrians, and passengers at risk, as it will likely cause an accident or run into different properties.

Before starting your trip, ensure all your truck brakes are working correctly. This includes service brakes, emergency brakes, and parking brakes. This applies to all types of trucks, whether light, medium, or heavy-duty.

5 Types of Service Brakes in Semi-Trailers

This list includes all the service brakes available for semi-trucks to operate effectively.

• Hydraulic brakes
• Drum brakes
• Disc brakes
• Combination brakes
• Air-over-hydraulic brakes

Components of a Braking System in Heavy-Duty Trucks

Here is a list of braking system components to inspect and determine if they work correctly. They include;

1. Brake pedals
2. Brake pads/shoes
3. Brake drums
4. Brake chambers

Indicators of a Faulty Braking System

Some of the signals of a failing brake system are;

Soft pedal feel. Soft brake pedals can occur for various reasons. These reasons include leaks in the brake master cylinder, rusty caliper parts, and the presence of air in the braking system. The air in the braking system can result from overheated calipers boiling the brake fluid.

When you apply the brakes, you can hear grinding, squeaking, or screeching noises. Worn-out brake pads produce these noises; to solve the problem, you need to replace them.

Brake warning lights. A red warning brake sign may appear on your dashboard to notify you of a problem with your truck’s braking system. You should not ignore such warning signals. Immediately pull over and determine the possible problem.

One-sided pulling. It happens when you apply brakes, and the brake pads and calibers on one side wear out. This causes the truck to pull to the opposite side with firm and strong brake pads or calibers. 

Vibrations or pulsations in the brake pedals. This can result from uneven wear on brake pads or twisted brake rotors.

Delayed stopping. Another signal of a faulty brake is that it takes a long time to stop after applying the brakes. This is dangerous because it can easily lead to fatal accidents.

If you have any of these problems, contact an expert to help curb them to prevent accidents.

3. Tire Systems

Tire systems on your semi-truck help you cover long distances while transporting cargo. If your tire has an issue, it delays movement. 

Check your tires before and after a trip to spot problems like misalignment and wear, and fix them as needed. This will ensure that your truck sails smoothly on upcoming trips.

What are The Signs of a Bad Tire Alignment?

Irregular tire wear. Uneven wear on tire edges could indicate misalignment and require adjustment. Check for feathering, scalloping, or cupping on the tire wheel.

You feel vibrations on the steering or the entire vehicle. Sometimes, you might experience vibrations on the steering wheel or the truck’s whole body when you increase the speed. 

This could be due to misaligned tires or any other issue. Always diagnose your vehicle to understand the exact cause of the problem.

Strange tire wear patterns on the trailer or drive axles. They indicate that your truck tires are misaligned and, therefore, need an adjustment.

Increased fuel consumption. Misaligned tires increase rolling resistance and consume a lot of fuel as they require extra power to pull over. 

Check if your truck tires are correctly aligned to improve fuel efficiency. If not, this could be the reason for decreased efficiency.

An off-center steering wheel. When the tires are correctly aligned on a straight road, the steering wheel should be at the center and straight. If your steering wheel constantly pulls to one side while driving straight, check if your tires are correctly aligned.

Pulling to one side. If your 18-wheeler keeps pulling to one side on a straight road, it indicates that your tires may be misaligned. 

Squealing sound. Nothing seems as disgusting as the squealing sound coming from your semi-truck. When turning or increasing the speed, the vehicle produces this sound.

4. Suspensions

Heavy-duty truck suspensions are crucial for smooth operation. They help contain road shocks and ensure the truck is stable on uneven roads and bumps. The trailer suspension is also essential to keep the rig’s axles in place.

There are four types of suspensions:

• Leaf spring. They are common in big-rig trucks and are attached to frames and movable parts, making them lengthy and variable. 
• Torsion bar. This suspension is used in some heavy-duty trucks where it is attached to the wishbone and twisted around the axle to provide suspension.
• Coil spring suspension. This type of suspension is common on trucks. It is easy to handle and will help you have a smooth ride. The coil suspension is similar to the leaf spring suspension, but instead of leaves, it uses metals.
• Air suspensions. These use airbags to support the cargo and can be adjusted to different road conditions. This type of suspension is found in luxury trucks and trailers.

Components of Truck Suspensions

Here are some essential parts to check and determine if your truck suspensions are working appropriately.

• Frames and chassis
• Coil springs
• Torsion bar struts
• Shock absorbers
• Rods and linkages
• Bushing, bearing, joints, and arms
• Rear leaf springs

Signs of a Faulty Suspension System in Your Tractor Trailer

Your truck is pulling to one side. Sometimes, worn-out ball joints, shock absorbers, and control arms may prevent your semi-truck from maintaining stability on the road.

Clunking or squeaking noise. A cracking sound produced when driving over potholes and bumps can signal that your shock absorbers, u-bolts, springs, bushings, arms, and other parts associated with your truck suspension have a problem that an experienced mechanic should address.

One side of the truck is lower than the other. A blown shock may increase pressure on the springs, compressing and lowering your vehicle's height while sitting. A broken spring can also result in a reduced height on one side.

Your semi-truck is taking a long time to come to a complete stop, swaying and leaning during turns. This is another sign of a suspension issue in your semi-truck, which may be faulty due to leaking shocks and other factors.

A malfunctioning steering wheel. The steering wheel may fail to function appropriately due to worn-out control arm bushing, low fluid in the steering, or leaking shock absorbers and struts. 

5. Electrical Issues.

The battery, the starter motor, and the alternator make up your 18-wheeler’s core complex electrical system. For it to operate effectively, the three must work together to power up and keep your truck running.

How the 3 work;

a). Your vehicle's battery powers many parts of your truck. It powers the starter motor, lights, radio, windshield wipers, locks, windows, air conditioning, and other electrical components on your truck's dashboard.

b). The starter motor converts that electrical energy to mechanical energy and supplies it to the engine to start it.

c). Finally, the alternator replenishes the battery and transmits electricity to the truck as the engine runs.

Signs of a Faulty Electrical System in Your 18-Wheeler

Your semi-truck engine may not start. This can result from a dead battery, an electrical connection issue, a failing starter, or a weak battery.

Smoke is coming from the starter circuit. This indicates a failing starter, poor wiring, or overheated wires.

Flickering lights. If your semi-truck lights are dim or flickering, it is a sign that your battery has an issue. Sometimes, this can be brought by a defective alternator and starter.

Dead battery. Your semi-truck battery may drain suddenly because of a faulty charging system, internal damage, or excessive electricity consumption.

Strange sounds. If your semi-truck produces a clicking, whining, cranking, or buzzing sound, it indicates a loose connection or a problem with your starter, alternator, or battery. 

Sulfur smell. You are likely to smell sulfur if your truck battery is leaking.

Your semi-truck engine is losing power. Sometimes, your engine may shut off abruptly. This can result from a failing alternator and battery.

6. Steering System

The steering system comprises components that must work harmoniously to enable your heavy truck to stay on the road and make appropriate turns to function correctly. 

The steering wheel helps the front wheels turn, allowing the car to cover long distances by transferring motion. 

The core components of a steering system include;

• Steering wheel
• Ball joints
• Pitman's arm
• Steering gearbox
• Kingpin
• Shims
• Front axle beam
• Steering column/shaft
• Spindle
• Tie rod and tie rod arms
• Rack and pinion
• Steering knuckle arm
• Idler arm

Signs of a Failing Steering System

If any steering system component has a problem, you will likely experience the following issues.

Loose steering wheel. You may notice your steering wheel slacking off. This can indicate worn-out ball joints, tie rod ends, and steering gears.

Difficulty and hard to turn. If your semi-truck steering wheel is stiff, this can result from a damaged power steering pump, low fluid, or defective steering gear.

Off-center steering wheel. You found yourself consistently turning the steering wheel to keep it at the center as it drifts to the opposite side. This can result from misaligned tires, steering linkage problems, or worn-out tires.

The clunking, squeaking, and grinding sounds are coming from the steering wheel. The sound is sometimes produced when the vehicle is at rest or when making turns. This can be due to a broken or worn-out power steering pump, tie rod end, or ball joints. 

Excessive vibrations from the steering wheel. You may experience increased shaking when turning your semi-truck wheels. This is an indicator that your steering is faulty.

Conversely, excessive vibrations can be caused by misaligned tires, worn-out bushings, control arms in the suspension, and twisted rims.

Steering fluid leaks. Sometimes, the power steering fluid reservoirs leak, releasing the steering fluid. If you notice the fluid in your semi-truck’s steering wheel, this could be due to worn-out hoses, seals, or even a faulty steering pump. 

Note: if you experience any of the above signs in your steering system, seek immediate help from an expert to avoid further damage or endangering your life and those around you.

7. Lighting Systems

Semi-trailers have different types of lights for various purposes. These lights will help you illuminate pathways and ensure your driver and other road users and drivers are safe. 

A faulty lighting system may cause fatal accidents or even make you struggle to see clearly in areas with mist and night hours.

Components of a Semi-Truck Lighting System

The following parts must be properly installed and connected for your 18-wheeler's lights to perform the various tasks they are designed for.

Battery. This is the source of electricity for your semi-truck lights.

Wiring straps. These are a group of wires that transfer electricity from the battery to the lights through the connectors.

Connectors. The connectors will join the electrical wires to the trailers and trucks' electrical systems so that they can operate smoothly.

Different Types of Big-Rig Lights

• Headlights
• Emergency and warning lights
• Trailer lights
• LED lights
• Off-road lights
• Fog lights
• Accessory lighting
• Tail lights
• Signal lights

Common Semi-Truck Light Issues

Dimming of headlights or internal lights. Your headlights may produce less light than their standard lighting, making you strain to navigate the road at night. This can be a result of an electrical problem or a failing battery.

Bulbs burn out and thus fail to turn on. This can be brought about by shaking or breaking filaments due to excessive vibrations, corrosion, and wiring issues.

Cracks and clouds on lenses. Clouds and cracks in your semi-truck light lenses indicate they have worn out, and you need to replace them to function efficiently. 

Misaligned headlights. The intense vibrations from trucks and trailers can sometimes loosen the grip of headlights, making them shake and fall out of alignment. This requires adjustment for them to function correctly.

8. Air Conditioning System (A/C)

An effective heating and cooling system in your truck will help you operate it during winter and summer and ensure you remain comfortable throughout the journey. 

Therefore, as a driver or truck owner, always check the status of your air conditioning system and ensure they are functioning well.

Your semi-truck air conditioning system is made up of the following;

• Compressor
• Condenser
• Evaporator
• Expansion valve
• Receiver/dryer
• Hoses/lines 

All these components work together to ensure better perform your A/C and semi-truck.

Signs of a Failing Air Conditioning System in Your Big Rig

A foul smell. Mold can cause your A/C system to release a bad smell. Dirty air filters and clogged evaporators are other possible reasons for that odor.

Presence of a black death in your A/C compressor. Typically, mold deposits from sludge or moisture are present in your compressor. The black substance can also be produced when introducing the wrong refrigerant to your vehicle or mixing non-compatible refrigerant oils.

Electric cooling fans may fail to function appropriately when your semi-truck is idle. This can be unnoticed when your truck moves quickly enough that air flows through the condenser to the grills. An overheating engine can cause the A/C to fail to perform its functions well.

Strange noise. Moreover, you may experience some unusual clanging or squealing noise when your A/C is on. This can be due to a loose belt, a damaged power motor, a broken expansion valve, or a worn-out compressor. 

Fluid leaks around the HVAC system. Punctures in the condenser and leaks in the hoses, compressors, evaporators, and O-rings, among other places, may cause your truck to lose refrigerant charge, thus lowering it. This will interfere with the smooth flow of the refrigerant oil.

Your semi-truck’s A/C is blowing warm or hot air. It is hot inside, and you want to use the A/C in your semi-truck to cool it down. However, the A/C is blowing warm air instead of cool air. Your A/C has a problem. 

You may have a faulty compressor, clogged expansion valves, damaged evaporator coils, disconnected wires, blown fuses, or low refrigerant oil.

Your A/C keeps running even after shutting off. You have turned off your air conditioner but realize it keeps running. The expansion valves are faulty. This will keep the refrigerant flowing to the compressor to keep it running.

Inconsistent air temperature. Your 18-wheeler may have varying temperatures in different vents, which signals low refrigerant levels in your A/C.

The compressor fails to start or stops unexpectedly. Let's get this right. You turn on your A/C, and the compressor fails to start, or maybe your A/C is running and stops suddenly. 

You might be confused, not knowing what is happening with the system. This might result from a blown fuse, a faulty thermostat, or a tripped circuit breaker.

9. Transmission System/Gearbox 

The transmission system is a gateway to the safe operation of your 18-wheeler. It is the driving force behind the engine and the vehicle's safe operation. 

As a truck driver, when you want to speed up or slow down your vehicle, you must reach out to the gearbox to achieve either. 

The gearbox is, therefore, part of the transmission system found in heavy-duty trucks and buses. It houses different types of gear that are responsible for changing the speed of your vehicle. 

This gearbox works in harmony with the clutch. Together, they help rotate the wheels, making turns transporting heavy loads from one destination to another.

Signs of a Faulty Transmission System in Your Semi-trailer

Transmission fluid leaks: If you observe transmission fluid leaks under your vehicle, it indicates that the gaskets and seals are worn out and need to be replaced.

Strange noises and vibrations: When shifting gears, you may hear a clunking, whining, or grinding noise. This may result from a worn-out torque converter, gears, and synchronizer rings.

Damaged seals and low transmission fluids may also cause unusual sounds in the transmission system.

Slip gear shifting: You may experience a delay in gear upshifting or downshifting, or gears may skip or stick, making it challenging to engage them properly. This may result from a damaged clutch, faulty solenoids, low transmission fluids, worn-out bands, and jammed gears.

Warning lights may appear on the dashboard: For instance, when the check engine light turns on, it could indicate a problem with the transmission system. In some modern semi-trucks, the transmission light may illuminate to alert you to abnormal transmission temperatures.

Overheating in the transmission: A burnt smell coming from your truck's transmission and engine system may be caused by excess friction or low transmission fluids. Overheating causes the fluids to burn out, releasing a foul odor.

Conclusion

Use this preventive maintenance checklist to find and fix any problems with your semi-truck. If you need help with any issues, contact a licensed mobile truck mechanic or visit a nearby truck repair shop. A well-maintained truck will safeguard your life, your driver's life, and other road users' lives. Regular maintenance can prevent your truck from breaking down while traveling, reduce downtime costs, and save money on future repairs or system replacements.

Frequently Asked Questions(FAQs)

1. What is a Preventive Maintenance Checklist for Semi-Trucks?

This checklist contains all the necessary maintenance steps for your semi-truck to function correctly. It helps prevent expensive breakdowns and accidents while on the road.

2. What Should Be Included in a Semi-Truck Maintenance Checklist?

Here are the items you should add to your semi-truck maintenance checklist for daily and periodic inspections.

a). Daily Inspection

Please remember to check the following items: tire pressure, wheel alignment, and inflation; gauges; windshield wipers; brakes; horn and backup alarms; oil leaks; mirrors; glass; rims; wheel lug nuts; grab handles; hydraulic systems; interior and exterior lights; heater and window defrosters; backup cameras; fuel tank; undercarriage and frame; seat structure; fire extinguisher; auxiliary system; and air conditioning system.

b). Periodic Maintenance

Oil filters, engine oil, transmission fluid, brake fluid, brake pads, air filters, hydraulic lines, drivelines, exhaust systems, and coupling devices.

3. Do Semi-Trucks Need Seasonal Maintenance?

Because of the different temperature ranges experienced throughout the year, you need to maintain your semi-trucks after every season. Adjusting your maintenance plan according to the climatic conditions will help you repair and maintain the affected parts and enable your truck to work efficiently.