MUFFLERS

Mufflers For Peterbilt Trucks

The muffler on a Peterbilt reduces exhaust noise to legal limits while managing exhaust backpressure -- two functions that affect both driver environment and engine performance. A muffler that's rusted through creates excessive noise and may cause cab exhaust intrusion. A muffler with significant internal restriction increases backpressure and reduces engine efficiency. We carry replacement mufflers for Peterbilt trucks in horizontal and vertical configurations to match your exhaust routing.

Frequently asked questions about mufflers

How do I know when a muffler needs to be replaced on my Peterbilt?

The most obvious indicator is increased exhaust noise -- a muffler that's rusted through or has an internal baffle failure will be noticeably louder than before, often with a raspy or hollow quality. Visible rust-through, cracks at the inlet or outlet welds, or a muffler body that crinkles when pressed are all signs of structural failure. On trucks where the muffler is in a location exposed to water and road debris accumulation, accelerated corrosion is common and should be inspected regularly on high-mileage trucks.

Does muffler style affect engine performance on a Peterbilt diesel?

Yes, to a degree. Muffler design affects exhaust backpressure, which in turn affects engine breathing and fuel efficiency. A muffler with excessive internal restriction increases backpressure beyond the engine's tolerance and can reduce power and fuel economy. Quality aftermarket mufflers designed for commercial diesel applications are flow-matched to minimize restriction while meeting noise requirements. Avoid mufflers designed for automotive applications on a heavy-duty diesel -- they're not designed for the flow volume and temperature of a large diesel engine.

What is the difference between a horizontal and a vertical muffler on a Peterbilt?

A horizontal muffler mounts parallel to the frame rail and is common on aerodynamic trucks like the 579 and 567 where a vertical stack would compromise aerodynamics. A vertical muffler (also called a stack) is mounted vertically with the exhaust exiting through the top, which is the classic look on conventional trucks like the 389. The exhaust routing and muffler mounting brackets are specific to each orientation, so confirm your current configuration before ordering a replacement.

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