2020 Ram 3500 Serpentine Belt Routing, Length, and Part Numbers

As an ASE-certified master technician, I see heavy-duty trucks like the 2020 Ram 3500 in the bay all the time. Whether your Ram is hauling heavy equipment or racking up highway miles, the serpentine belt is the lifeline for your engine’s accessories. A snapped belt on a 6.7L Cummins or 6.4L HEMI means a sudden loss of charging, cooling, and air conditioning.

Below is your comprehensive reference guide for the 2020 Ram 3500 serpentine belt, focusing on the most common 6.7L Cummins Turbo Diesel (Single Alternator) configuration.

Quick answer

Note: The following specifications are for the 2020 Ram 3500 equipped with the 6.7L Cummins Turbo Diesel (Single Alternator). If you have the 6.4L HEMI V8 or a dual-alternator Cummins setup, your part numbers and belt lengths will differ.

• Rib Count: 8-rib (Heavy Duty)
• Belt Length: 82.3 to 82.5 inches (effective length)
• OEM Belt Part Number: Mopar 68285082AA
• Aftermarket Cross-References: Gates K080823HD (Heavy Duty Green), Dayco 5080825, Continental 4080825
• Auto-Tensioner Part Number: Mopar 53045293AA (Gates 38656)
• Idler Pulley Part Number: Mopar 53045294AA (Gates 36365)

Belt routing

Since we cannot render an image, it is crucial that you carefully read this text-based step-by-step description of the routing path for the 6.7L Cummins (single alternator). Always photograph your existing belt before removal to ensure you have a visual reference specific to your exact truck's configuration.

For the standard 6.7L Cummins, the ribbed side of the belt will ride on grooved pulleys, while the smooth side rides on smooth pulleys (like the idler and tensioner).

1. Start by looping the belt around the bottom of the Crankshaft pulley.
2. Bring the belt straight up on the left side (passenger side) to wrap over the Water Pump / Fan pulley.
3. From the water pump, route the belt across to the Alternator.
4. Pull the belt down from the alternator and loop it around the A/C Compressor.
5. Route the smooth back of the belt under the Idler pulley.
6. Finally, pull the remaining slack over the Auto-Tensioner pulley. You will need to release the tensioner to slide the belt onto this final pulley.

How to replace the serpentine belt

Replacing the belt on a 2020 Ram 3500 requires dealing with tight clearances, especially around the fan shroud on the Cummins engine.

1. Gather your tools: You will need a dedicated serpentine belt tool or a long 3/8" (or 1/2" depending on the tensioner brand) breaker bar to leverage the tensioner.
2. Relieve tension: Locate the auto-tensioner on the front of the engine block. Insert your breaker bar into the square drive hole on the tensioner arm. Rotate the tensioner to relieve the pressure on the belt.
3. Remove the old belt: Slip the belt off the easiest accessible pulley (usually the alternator or A/C compressor) while holding the tensioner open. Carefully release the tensioner and weave the old belt out from around the cooling fan.
4. Inspect pulleys: Spin the idler, tensioner, alternator, and A/C pulleys by hand. Listen for grinding bearings and check for excessive play.
5. Install the new belt: Route the new belt according to your reference photo and the routing steps above. Leave the tensioner pulley for last.
6. Apply tension: Rotate the tensioner again with your breaker bar, slip the belt over the final pulley, and slowly release the tensioner. Double-check that the belt is seated perfectly in all the grooves of every ribbed pulley before starting the engine.

Replacement interval

For heavy-duty applications like the Ram 3500, preventative maintenance is key. Serpentine belts should be thoroughly inspected every 30,000 miles. Standard replacement intervals are typically between 60,000 and 90,000 miles. However, if your truck idles extensively, operates in severe dusty conditions, or tows heavy loads daily, you should plan to replace the belt and the tensioner closer to the 60,000-mile mark. Modern EPDM belts do not crack as visibly as older neoprene belts; instead, the ribs wear down like tire tread.

Signs of a failing belt or tensioner

Don't wait for the belt to snap on the highway. Watch for these common warning signs:

• Squealing or chirping: A high-pitched noise on startup or under heavy electrical loads usually indicates a stretched belt, a weak tensioner spring, or a failing pulley bearing.
• Visible wear: Look for missing rib sections, fraying edges, or a glazed, shiny appearance on the belt surface. Use a belt wear gauge to check rib depth.
• Tensioner bounce: With the engine running, observe the tensioner arm. A slight vibration is normal, but excessive jumping or bouncing means the internal damping mechanism has failed.
• Heavy steering or overheating: If the belt is slipping badly, the water pump and other accessories won't spin at their optimal speeds, leading to temperature spikes or warning lights on your dash.

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