2015 GMC Sierra 2500HD Serpentine Belt Routing & Length

Quick Answer

The 2015 GMC Sierra 2500HD (with the 6.0L V8 or 6.6L Duramax Diesel) utilizes a multi-rib serpentine belt to power its accessories. There are two different belt systems depending on the engine.

6.0L Vortec V8 (Gasoline)

• Belt Length: Approximately 98 inches (main drive belt)
• Rib Count: 6-rib
• OEM Belt PN: AC-Delco 6K983
• Aftermarket Cross-references:
  • Gates K060983
  • Dayco 5060983
  • Continental Elite 4060983
• Auto-Tensioner PN: AC-Delco 38328 / Gates 38328
• Idler Pulley PN: AC-Delco 38006 / Gates 38006

6.6L Duramax Diesel (LML)

• Belt Length: Approximately 93.3 inches (main drive belt)
• Rib Count: 6-rib
• OEM Belt PN: AC-Delco 6K933
• Aftermarket Cross-references:
  • Gates K060933
  • Dayco 5060933
  • Continental Elite 4060933
• Auto-Tensioner PN: AC-Delco 38243 / Gates 38243
• Idler Pulley PN: AC-Delco 38006 / Gates 38006

Belt Routing

Before you begin any belt removal or replacement, it is highly recommended to take a clear photograph of the existing belt's routing path from multiple angles. This will serve as an invaluable reference during reinstallation, as attempting to route a serpentine belt without a visual guide can be frustrating. The serpentine belt drives multiple accessories, and mis-routing can lead to damage or immediate malfunction.

6.0L Vortec V8 Routing (Common Configuration)

1. Begin at the Crankshaft Pulley (bottom center of the engine), routing the belt over the top of the pulley.
2. From the Crankshaft Pulley, the belt travels upwards to the A/C Compressor Pulley (typically on the lower passenger side of the engine), wrapping around its top.
3. From the A/C Compressor, the belt goes to an Idler Pulley (often located above the A/C compressor), wrapping around its bottom.
4. From the Idler Pulley, the belt then heads upward to the Alternator Pulley (typically on the upper driver's side of the engine), wrapping around its top.
5. Next, the belt goes downwards to the Power Steering Pump Pulley (usually below the alternator), wrapping around its bottom.
6. From the Power Steering Pump, the belt routes to the Water Pump Pulley (often near the center top of the engine, below the fan clutch), wrapping around its top.
7. Finally, the belt runs from the Water Pump pulley to the Automatic Tensioner Pulley (typically on the lower driver's side of the engine), wrapping around its bottom. The tensioner will have a square drive hole for a serpentine belt tool or breaker bar.

6.6L Duramax Diesel Routing (Common Configuration)

1. Start at the Crankshaft Pulley (bottom center front of the engine), routing the belt over the top.
2. From the Crankshaft Pulley, the belt goes to the A/C Compressor Pulley (lower passenger side), wrapping around its top.
3. Next, it travels to an Idler Pulley (often slightly above the A/C compressor), wrapping around its bottom.
4. The belt then goes to the Alternator Pulley (upper passenger side), wrapping around its top.
5. From the Alternator, the belt descends to the Water Pump Pulley (center of the engine, below the fan hub), wrapping around its top.
6. Next, the belt routes to the Power Steering Pump Pulley (upper driver's side), wrapping around its top.
7. Finally, the belt goes to the Automatic Tensioner Pulley (lower driver's side), wrapping around its bottom. This is where you'll apply tension to remove or install the belt.

How to Replace the Serpentine Belt

Replacing a serpentine belt on your 2015 GMC Sierra 2500HD is a manageable DIY task, but requires the correct tools and attention to detail.

Tools Needed:

• Serpentine belt tool or a 3/8" drive breaker bar (for the tensioner)
• Socket set (if removing idler pulleys for inspection)
• New serpentine belt

Steps:

1. Safety First: Ensure the engine is cool and the vehicle is in Park (automatic) or Neutral (manual) with the parking brake engaged. You may want to disconnect the negative battery terminal to prevent accidental starting.
2. Document Routing: As mentioned, take several photos of the existing belt routing pattern.
3. Relieve Tension: Locate the automatic belt tensioner. Insert your serpentine belt tool or a 3/8" drive breaker bar into the square drive hole on the tensioner arm. Rotate the tool/bar to release tension on the belt. This will typically be counter-clockwise, but observe the tensioner's movement.
4. Remove Old Belt: While holding the tensioner open, carefully slip the old belt off one of the pulleys (e.g., the alternator or idler pulley). Once it's off one pulley, you can slowly release the tensioner and remove the belt completely.
5. Inspect Pulleys: With the belt removed, manually spin each pulley (alternator, A/C compressor, power steering pump, water pump, idlers). Listen for any grinding, squealing, or roughness, and check for excessive wobble. Replace any worn idler pulleys or other components at this time.
6. Install New Belt: Route the new belt around all pulleys according to your photographs, leaving the tensioner pulley for last or a pulley that is easy to slip on. Once the belt is mostly in place, use your serpentine belt tool/breaker bar to again release the tensioner. Slip the remaining part of the belt onto the tensioner pulley. Double-check that all ribs of the belt are seated correctly in all pulley grooves.
7. Verify Routing: Ensure the belt routing precisely matches your photos and the diagram printed under the hood (if available).
8. Test: Start the engine and listen for any abnormal noises (squealing, chirping). Observe the belt for any signs of misalignment or wobble. Turn the steering wheel from lock to lock and cycle the A/C to ensure all accessories function correctly.

Replacement Interval

Manufacturers often recommend inspecting serpentine belts every 60,000 miles and replacing them as necessary, or proactively replacing them between 75,000 to 100,000 miles. However, these are general guidelines. Factors like extreme temperatures, dusty conditions, and fluid leaks (oil, coolant, power steering fluid) can significantly accelerate wear. It's always best to follow your owner's manual for specific recommendations for your 2015 GMC Sierra 2500HD.

Signs of a Failing Belt or Tensioner

Ignoring a failing serpentine belt or tensioner can lead to a roadside breakdown, as accessories like the alternator, power steering, and water pump will cease to function. Here are the warning signs to watch for:

• Squealing or Chirping Noises: This is the most common symptom. It often indicates a stretched belt, a misaligned pulley, or a failing tensioner that isn't applying enough pressure.
• Visible Cracks or Fraying: Cracks along the ribbed surface, missing chunks of ribs, or frayed edges are clear indicators the belt is at the end of its life and needs immediate replacement.
• Glazed or Shiny Belt Surface: A shiny, glazed appearance on the belt ribs suggests the belt is slipping, often due to age, wear, or improper tension.
• Loss of Power Steering: If your power steering suddenly becomes heavy and difficult to turn, the serpentine belt may have slipped or broken.
• Overheating Engine: The water pump, which circulates coolant, is driven by the serpentine belt. If the belt fails, the engine can quickly overheat.
• Battery Light On/Dead Battery: The alternator, which charges the battery, is also driven by the serpentine belt. A broken or slipping belt will prevent the battery from charging.
• A/C Not Working: The air conditioning compressor relies on the serpentine belt. If your A/C stops blowing cold, a belt issue could be the cause.
• Grinding or Rattling from Tensioner/Idlers: Noises coming from the tensioner or idler pulleys can indicate worn bearings, meaning these components need to be replaced along with the belt.
• Excessive Belt Slack: If the belt appears unusually loose or has significant play, the automatic tensioner may be failing and no longer applying the correct tension.

Don't wait for a complete failure. Address these symptoms promptly to maintain the reliability of your pickup.

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