2015 Ram 3500 — Serpentine Belt Routing & Length

Quick answer

• Belt length and rib count
  • 6.7L Cummins (single alternator, with A/C): typically about 100.5 in length; 6‑rib (verify by VIN/build)
  • 6.7L Cummins (dual alternators): uses main belt plus a secondary alternator belt; lengths vary by build (verify by VIN/build)
  • 6.4L Hemi V8 (gas): commonly 7‑rib; length varies by pulley package (verify by VIN/build)
• OEM belt part number (Mopar): varies by engine (6.7L Cummins vs. 6.4L Hemi), A/C, and single vs. dual alternator. Use your VIN at a Mopar/Chrysler-Ram parts counter to confirm the exact PN.
• Aftermarket cross‑references (examples for 6.7L Cummins, single alternator w/ A/C – confirm by VIN):
  • Gates: K061005
  • Dayco: 5061005
  • Continental: 4061005
• Automatic tensioner PN: varies by engine and accessory package; confirm by VIN (do not order by guesswork)
• Idler pulley PN: varies by engine and accessory package; confirm by VIN

Note: The 2015 Ram 3500 was sold with multiple accessory layouts. Always verify with VIN or by measuring/removing the current belt and matching the imprint on the old belt.

Belt routing

Because we can’t include an illustration here, photograph your current belt routing before removal. On the common 6.7L Cummins single‑alternator setup with A/C, the routing follows this path when viewed from the front of the truck:

Crankshaft pulley → A/C compressor → lower idler → alternator → power steering pump → water pump → automatic tensioner → back to the crankshaft pulley.

Tips:

• The back (smooth) side of the belt rides on smooth pulleys like the water pump and some idlers; the ribbed side rides on grooved pulleys like the crank, alternator, A/C, and power steering.
• If your truck has the dual‑alternator package, there is an additional, shorter belt for the second alternator and a different main‑belt path. Follow the under‑hood decal or service manual for that configuration.

How to replace the serpentine belt

Tools and prep:

• Serpentine belt tool or 3/8" breaker bar for the tensioner square drive
• Flashlight and a routing reference photo
• New belt (and consider new tensioner/idler(s) if the truck has high mileage)

Steps:

1. Disconnect the negative battery cable(s) if you’ll be working near the fan or moving pulleys for an extended time.
2. Locate the automatic tensioner and its 3/8" square drive boss. Insert the serpentine belt tool or breaker bar and rotate the tensioner to relieve belt tension.
3. While holding tension off, slip the belt off one easy‑to‑reach grooved pulley (often the alternator).
4. Slowly release the tensioner to its rest position.
5. Compare the old belt length/rib count to the new one. If the old belt’s printing is legible, note the number (e.g., 6PK2550 ≈ 6 ribs, 2550 mm).
6. Route the new belt per the path above, leaving the easiest pulley for last. Ensure ribs are fully seated in every grooved pulley.
7. Rotate the tensioner again and slide the belt over the final pulley. Release the tensioner slowly.
8. Double‑check alignment on every pulley. A single rib off will shred a belt quickly.
9. Start the engine and watch the belt for one full minute. Look for tracking issues or tensioner “bounce.” Shut down and re‑inspect if anything looks off.

Replacement interval

• Inspect at every oil change; replace around 60,000–90,000 miles under typical use. Heavy towing, dusty/farm use, or extreme temps may shorten the interval.
• Replace the automatic tensioner and idler pulleys between 100,000–150,000 miles or whenever you replace a severely worn belt, hear bearing noise, or see tensioner instability.

Signs of a failing belt or tensioner

• Belt: glazing (shiny ribs), cracks across the ribs, chunking, frayed edges, or contamination from oil/coolant.
• Noise: cold‑start chirp or continuous squeal, especially with A/C on or while steering at low speeds.
• Charging/overheat warnings: battery light flicker, dim lights at idle, rising coolant temps, or heavy steering effort can indicate slip.
• Tensioner/idler issues: pulley wobble, gritty or rough rotation by hand, or tensioner arm that chatters/bounces at idle.

Engine and option variations to watch

• 6.7L Cummins: offered with single or dual alternators; belt length and routing differ. Some fleet packages use different idler/tensioner hardware.
• 6.4L Hemi gas: generally uses a 7‑rib belt and a different routing. Some builds without A/C have a shorter belt and an A/C‑bypass idler.
• Always match by VIN, build sheet, or the under‑hood belt‑routing decal. If the truck lacks a decal, decode the existing belt’s part number or measure the old belt and count ribs.

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