What Are the Most Common Repairs for Class 8 Trucks?

When you're clocking serious miles behind the wheel of a Class 8 truck, breakdowns aren't a matter of "if", they’re a matter of "when." These 33,000+ lb machines haul everything from heavy machinery to fresh produce. But their size and stamina come with a price: wear and tear that can put you on the side of I-15 faster than you can say "check engine light."

That’s why we’ve asked our team what the most common repairs for Class 8 trucks are.

1. Brake System Repairs

Brake issues are hands down one of the most frequent repairs we see for heavy-duty trucks. With the sheer weight they carry, especially on Nevada's steep grades, brakes take a serious beating. 

Unlike light vehicles that use hydraulic brakes, Class 8 trucks rely on compressed air brake systems, a complex setup involving air compressors, slack adjusters, service chambers, and more.

Common repairs:

• Slack adjuster replacement
• S-cam wear
• Brake shoe and drum resurfacing or replacement
• Air line leaks or freeze-ups
• Faulty air dryers are allowing moisture buildup

You’ll often notice symptoms like poor stopping power, squealing, or pulling to one side; don’t wait for these. At 80,000 pounds, delayed braking could be deadly.

2. Diesel Engine Troubles

Diesel engines are rugged but far from invincible. Whether it’s Cummins, Detroit, or PACCAR, problems often boil down to fuel system issues, EGR valve failures, or oil pressure drops.

Frequent engine repairs include:

• Fuel injector replacement
• Turbocharger failures
• Glow plug malfunction
• Oil pump failure
• Cooling system repairs due to cracked hoses or bad water pumps

If you’re seeing white smoke, losing power, or burning oil, don’t ignore it. North Las Vegas temperatures can be brutal on engines, and the desert doesn’t do favors for overheating trucks.

3. Transmission Failures

Transmission problems are no joke, especially when you're hauling up the mountainous Nevada terrain. Whether you run a manual, automated manual, or automatic transmission, you’ll eventually face issues like gear slipping, overheating, or rough shifting.

Most common fixes:

• Clutch adjustments or replacements (manual)
• Transmission fluid flushes or leak repairs
• ECU reprogramming (AMTs)
• Torque converter failures

Keep an eye out for sluggish acceleration or gears refusing to engage. That’s your signal to visit the shop—before a minor grind turns into a total rebuild.

4. Suspension and Steering Component Wear

Nevada highways aren’t always kind, and years of bouncing over potholes and rail crossings wreak havoc on your suspension system. For Class 8 trucks, it usually comes down to leaf spring damage, air suspension leaks, or worn shocks.

Repairs you’ll likely face:

• Replacing leaf spring hangers or cracked springs
• Airbag repairs or compressor issues
• Shock absorber replacement
• Worn kingpins or tie rods

Symptoms like bouncy rides, vehicle leaning, or steering play shouldn't be ignored. These are often the first warning signs of more costly damage down the line.

5. After-Treatment System Failures (DPF, SCR, EGR)

Emissions equipment is both a blessing and a curse. While they keep the air cleaner, these after-treatment systems (like the DPF, SCR, and EGR) are notorious for causing downtime.

Typical problems:

• Clogged DPF needing forced regeneration
• EGR cooler failure
• DEF dosing pump issues
• SCR catalyst degradation

You might see warning lights, poor fuel economy, or limp mode activation. And here in North Las Vegas, heat can accelerate sensor and DEF issues if left unchecked.

6. Cooling System Failures

An overheating engine is a Class 8 trucker’s nightmare, especially under the Mojave sun. The cooling system includes your radiator, coolant lines, thermostat, and fan clutch, all working overtime to keep things chill.

Usual suspects:

• Cracked radiator tanks or hoses
• Failed fan clutch
• Plugged radiator fins
• Faulty water pump
• Low coolant due to leaks

If your temperature gauge is creeping into the red, pull over. An overheated engine can blow head gaskets or warp components, quickly turning a $200 repair into a $10,000 one.

7. Electrical and Charging System Issues

Modern Class 8 trucks are equipped with a complex network of electronics, from sensors and telematics to ECUs and advanced safety systems. Electrical gremlins can grind your route to a halt in a flash.

Most common repairs:

• Starter motor or alternator failure
• Shorted wiring harnesses
• Sensor replacements (especially NOx and DPF sensors)
• Battery and cable corrosion

Symptoms range from slow starts and dead batteries to warning lights lighting up like a Christmas tree. Regular diagnostic scans can catch these before they leave you stranded.

8. Wheel-End Repairs and Bearing Failures

Wheel bearings do a critical job, keeping your wheels spinning smoothly under massive loads. But once they go bad, they can generate heat fast, sometimes to the point of seizing the wheel assembly.

Signs and fixes include:

• Overheating wheel hubs
• Loud grinding or screeching
• Bearing repacking or replacement
• Axle seal leaks

Left untreated, a failed bearing can weld itself to the spindle, meaning full hub replacements and major downtime.

Conclusion: Know What to Expect, Stay Ready

Class 8 trucks are workhorses, but even the toughest rigs need care. Brake systems, engines, transmissions, cooling components, and emissions equipment make up the lion’s share of repairs. 

Whether you’re running freight across I-15 or grinding through stop-and-go routes near Las Vegas, staying on top of these issues is the best way to keep your wheels rolling and your load on time.

Need help staying ahead of the curve? Don’t wait until you're sidelined. Schedule your next inspection or maintenance check today!