The pulley can do more than spin
An overrunning alternator pulley allows the alternator to freewheel during deceleration. Decoupler designs can also provide vibration isolation in the accessory drive. A pulley that looks dimensionally similar may not perform the same function.
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Match the original drive design
Identify the vehicle’s specified pulley type when replacing the alternator or pulley. Do not substitute a solid pulley merely because the belt fits. Use the correct holding tools and installation instructions for the replacement assembly.
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Inspect the neighboring parts
Check the belt, tensioner and idlers as part of the diagnosis. Abnormal drive movement or noise can involve more than one component. Keep hands and tools away from a running belt and have operating observations performed safely by a technician.
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Sources / references 1
- Manufacturer technical reference ↗Reviewed Oct 6, 2026
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