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Front End Accessory Drive System Maintenance for Heavy Duty Trucks

Inspect Belts During Oil Changes, Replace at 300,000 Miles

Just like many other components on today’s class 4-8 trucks, it’s important that mechanics look at the belt, pulleys and tensioner as a whole system and replace all components at once. Called the front-end accessory drive system (or FEAD for short), most commercial vehicle OEMs recommend inspections during oil changes, or at around 100,000 miles, and full replacement around 300,000 miles. All three components experience wear and tear gradually over time so replacing the two pulleys, tensioner and belt altogether will allow for more enhanced performance. It’s important to note that if just the belt is replaced, the truck may experience a loose tensioner or pulley within a short period of time, and may require another belt due to premature failure.

Front End Drive System Warning Signs

If a technician is unsure whether a big rig’s FEAD system needs replacement, here are two key warning signs:

1. Heavy Duty Truck Belt Noise

Different noises correlate to different problems. Spray water on the belt with the engine running and then listen for one of these two sounds.

  • Chirp – Intermittent noises that are sharp, as belt speed increases pitch and volume stay constant. A chirp is often the result of misalignment, improper installation or worn parts. If this noise continues with a light spray of water, further investigation is needed to determine the cause of misalignment.
  • Squeal – High pitched noise that lasts several seconds and doesn’t change in pitch. It may change with acceleration or an added accessory load. If the noise goes away with a light water spray, it is usually a sign of tension loss.

2. Heavy Duty Belt Alignment

A technician should examine the way the belt tracks. If it is tracking off center, at or off the edge of the pulley, or if the belt flips off the tensioner, this could be a sign of tensioner misalignment caused by bushing wear.

Belt, Tensioner and Pulley Replacement a Best Practice

Replacing all the components at the same time enables mechanics to ensure the front-end accessory drive system is completely aligned. Checking and replacing the belt alone could be problematic as it rarely solves the vehicle’s issue. In an effort to avoid downtime, replace the tensioner assembly and associated pulleys when the belt is changed.