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Dayco 89478 Accessory Drive Belt Tensioner Assembly
| Brand | Dayco 89478 |
|---|---|
| Position | Fan and Alternator, Alternator, Water Pump, Fan, and Main Drive |
| Belt Type | Serpentine |
| Direction | Counter clock wise |
| Number of Pulleys | 1 |
| Pulley 1 Diameter | 74 |
| Pulley 1 Flat | Y |
| Pulley 1 Width | 39.25 |
| Type | Automatic |
| Fits | — |
Automatic tensioner assembly. Maintains proper serpentine belt tension for consistent drive performance.
Single-pulley design. Uses one pulley for a straightforward, compact belt drive setup.
Serpentine belt compatible. Built for accessory drive systems that use a serpentine belt.
Cross-references ACDelco 38504, CARQUEST 38504 and Case 87326910 for the same application. See all 43.
Accessory Drive Belt Tensioner for Serpentine Systems
The Dayco 89478 accessory drive belt tensioner assembly is built for serpentine belt systems that require automatic belt control and consistent pulley alignment. It features a counter clockwise rotation, a single pulley, and a flat pulley face to support stable belt tracking in the accessory drive system.
Use this Dayco tensioner assembly when servicing accessory drive belt noise, belt slack, or tension-related wear on compatible Cummins, Case, and Komatsu applications. The 89478 is also cross-referenced to ACDelco 38504 and Gates 38504 for the same application.
Key Features
- Brand: Dayco
- Part number: 89478
- Accessory drive belt tensioner assembly
- Serpentine belt type
- Automatic tensioner design
- Counter clockwise rotation
- Single pulley construction
- 74 mm pulley diameter
- 39.25 mm pulley width
- Flat pulley surface for belt contact
Detailed Description
Dayco 89478 is an automatic accessory drive belt tensioner assembly engineered for serpentine belt routing in heavy-duty and industrial accessory drive systems. The pulley measures 74 mm in diameter with a 39.25 mm width and a flat running surface, helping maintain proper belt engagement as the system operates. This part number 89478 is listed with interchange references including ACDelco 38504, CARQUEST 38504, and Gates 38504.
For buyers searching by vehicle or equipment keywords, this tensioner is associated with Cummins, Case, CNH, and Komatsu applications. If you are replacing a worn belt tensioner on a Cummins-powered machine or servicing a Case or Komatsu accessory drive belt system, Dayco 89478 is a direct replacement-style option to compare against the original assembly.
What It Helps Address
- Belt squeal caused by weak or inconsistent tension
- Accessory drive belt flutter or vibration
- Premature serpentine belt wear from poor pulley control
- Noise from a worn tensioner pulley or bearing
- Loss of belt tracking in the accessory drive system
Installation Notes and Tips
Verify belt routing, pulley rotation direction, and pulley alignment before installation. Confirm the existing tensioner matches the counter clockwise configuration and the pulley dimensions listed for Dayco 89478. Inspect the serpentine belt, idler pulleys, and adjacent accessory drive components at the same time to avoid repeat service.
Quality Assurance
Dayco is a recognized name in belt drive components, and this tensioner assembly is specified with clear dimensional and rotational details to support accurate replacement selection. Confirm fitment by part number and application data before installation.
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|---|---|---|---|---|
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