2017 GMC Sierra 2500HD Serpentine Belt Routing & Length

Quick Answer

The 2017 GMC Sierra 2500HD, when equipped with the popular 6.6L Duramax Diesel (LML/L5P) or 6.0L Vortec gasoline engine, utilizes a serpentine belt system that is critical for powering various engine accessories. It's crucial to verify your specific engine configuration for accurate part numbers, as there can be slight variations.

Here are the typical specifications for the 6.6L Duramax Diesel (L5P/LML - most common for 2017 2500HD):

• Belt Length: Approximately 106.5 inches (2705 mm)
• Rib Count: 6-Rib
• OEM Belt PN: AC-Delco 12658862 (Verify with VIN)
• Aftermarket Cross-References:
  • Gates K061065
  • Dayco 5061065
  • Continental Elite 4061065
• Auto-Tensioner PN: AC-Delco 12635467 (for 6.6L Duramax - Verify with VIN)
• Idler Pulley PN: AC-Delco 12628469 (for 6.6L Duramax - Verify with VIN)

For the 6.0L Vortec Gasoline engine, specifications will differ. Always confirm with your VIN.

Belt Routing

Before you begin any work, take a clear photograph of your existing serpentine belt routing. This will serve as an invaluable reference during reinstallation. The 2017 GMC Sierra 2500HD's serpentine belt effectively powers the alternator, power steering pump, air conditioning compressor, and water pump. While exact routing can vary slightly by engine and accessory options, a common path for the 6.6L Duramax (and similar for the 6.0L Vortec) would be as follows:

1. Begin at the Crankshaft Pulley, which is the large pulley at the bottom, centered on the front of the engine, providing power to the entire system.
2. From the crankshaft, the belt typically goes UP to the A/C Compressor Pulley, usually located on the lower passenger side of the engine.
3. After the A/C compressor, the belt routes OVER an Idler Pulley, which is a smooth pulley providing tension and guiding the belt, often found near the center-upper part of the belt path.
4. From the idler, the belt continues UP to the Alternator Pulley, prominently located at the top of the engine compartment, usually on the driver's side.
5. Next, the belt routes DOWN to the Power Steering Pump Pulley, typically situated below the alternator.
6. The belt then moves ACROSS the front of the engine to the Water Pump Pulley, often found in the center-top area of the engine, driving the engine's coolant circulation.
7. Finally, the belt makes its way DOWN to the Automatic Tensioner Pulley, which will have an arm that pivots to maintain correct belt tension. This is usually located on the lower driver's side, or near the crank pulley.

Remember to consult your vehicle's service manual or a diagram specific to your engine for the most accurate routing.

How to Replace the Serpentine Belt

Replacing the serpentine belt on your 2017 GMC Sierra 2500HD is a moderately challenging DIY task. You will need a specialized serpentine belt tool or a 3/8-inch drive breaker bar / long ratchet. The key is to relieve the tension from the automatic tensioner.

1. Safety First: Disconnect the negative battery terminal. Ensure the engine is cool.
2. Locate the Tensioner: Identify the automatic belt tensioner. It will have a square hole (usually 3/8" or 1/2") or a hex bolt head where you can apply leverage.
3. Relieve Tension: Insert your serpentine belt tool or breaker bar into the tensioner's square hole/bolt head. Rotate the tensioner clockwise (or counter-clockwise, depending on the design – observe the tensioner's arm movement) to release the tension on the belt. This will allow you to slip the belt off the pulleys.
4. Remove Old Belt: While holding the tensioner open, carefully slip the old belt off one or two pulleys (the idler pulley is often easiest to start with) and then remove it completely.
5. Inspect Pulleys: This is an excellent time to inspect all pulleys (alternator, power steering, A/C compressor, water pump, idler, and tensioner) for any excessive play, wobbling, or grinding noises. Replace any worn pulleys.
6. Route New Belt: Following your photograph and the routing description above, carefully route the new belt around all pulleys except for one easy-to-access pulley (again, often an idler or the smooth tensioner pulley itself).
7. Final Tensioning: Once the belt is mostly routed, use your tool to again rotate the tensioner, creating slack. Slip the new belt over the last pulley. Carefully release the tensioner, ensuring the belt seats correctly in all grooves.
8. Double-Check: Visually inspect to make sure the belt is perfectly seated in all pulley grooves and that there are no twists or kinks.
9. Reconnect Battery: Reconnect the negative battery terminal. Start the engine briefly and listen for any unusual noises. Turn off the engine and re-check the belt routing.

Replacement Interval

While there isn't a universally strict replacement interval for serpentine belts, general recommendations for the 2017 GMC Sierra 2500HD (and most modern vehicles) suggest inspection every 30,000 to 50,000 miles and replacement every 60,000 to 100,000 miles, or every 5-7 years, whichever comes first. However, driving conditions, engine type, and belt material can influence this. Always refer to your owner's manual for the manufacturer's specific recommendations.

It is often a good practice to replace the automatic belt tensioner and idler pulleys at the same time as the belt, especially if they show any signs of wear, as they are critical to the belt's proper function and lifespan.

Signs of a Failing Belt or Tensioner

Ignoring a failing serpentine belt or tensioner can lead to significant problems, as many critical engine components rely on this belt. Be vigilant for the following signs:

• Squealing or Chirping Noises: This is the most common symptom. It often indicates a loose, worn, or misaligned belt, or a failing tensioner or pulley bearing. The sound may be more pronounced on cold starts or when turning the steering wheel.
• Cracks, Fraying, or Glazing on the Belt: Visually inspect the belt. Deep cracks, missing chunks, frayed edges, or a shiny, smooth (glazed) appearance on the ribbed side are all indicators that the belt needs replacement.
• Loss of Power to Accessories: If your power steering suddenly becomes heavy, the A/C stops blowing cold, or the battery warning light comes on (indicating the alternator isn't charging), it could mean the serpentine belt has slipped or broken.
• Vibrations or Wobbling: A failing tensioner can cause excessive vibration in the belt, or you might notice the tensioner arm or an idler pulley wobbling while the engine is running.
• Grinding Noises from Pulleys: This often points to a worn-out bearing within the tensioner or an idler pulley, which will eventually lead to belt failure.
• Steering Difficulty: A sudden increase in effort required to turn the steering wheel is a strong indicator of an issue with the power steering system, often caused by a failing serpentine belt.

If you notice any of these symptoms, it's best to address the issue promptly to prevent further damage or being stranded.

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