2020 Ram ProMaster Serpentine Belt Routing & Part Numbers

As an ASE-certified master technician, I know that keeping up with routine maintenance on your commercial fleet or personal cargo van is critical for avoiding costly downtime. The 2020 Ram ProMaster, heavily relied upon by tradespeople and delivery services, is primarily equipped with the workhorse 3.6L Pentastar V6 engine. The serpentine belt on this engine drives all your crucial accessories, and knowing the exact routing, specifications, and replacement procedures will save you time and headaches.

Here is your comprehensive serpentine belt reference guide for the 2020 Ram ProMaster (3.6L V6).

Quick answer

When it’s time to source parts for your 2020 ProMaster 3.6L V6, use these verified specifications and part numbers:

• Rib Count: 6-rib design
• Belt Length: Approximately 67.8 inches (1722 mm) effective length
• OEM Belt Part Number: Mopar 05122441AB (or updated AD suffix)
• Aftermarket Belt Cross-References: Gates K060678, Dayco 5060678, Continental Elite 4060678
• Auto-Tensioner Part Number: Mopar 5186251AA (Aftermarket: Gates 39768 / Dayco 89552)
• Idler Pulley Part Number: Mopar 05186255AA (Aftermarket: Gates 36329)

Note: If your ProMaster happens to be the rare 3.0L EcoDiesel (discontinued for 2020 but sometimes registered late), specifications will differ drastically. The information below applies specifically to the standard 3.6L Pentastar V6.

Belt routing

Because the 3.6L V6 in the ProMaster is mounted transversely (sideways) for the front-wheel-drive architecture, working space is relatively tight against the passenger-side frame rail. Always photograph or sketch the existing belt routing before removal—it’s easy to forget which side of a smooth pulley the belt rides on once it is off!

For the 3.6L V6 ProMaster, follow this text-based step-by-step routing path:

1. Start by looping the ribbed side of the belt around the bottom of the Crankshaft Pulley.
2. Route it straight up to the A/C Compressor.
3. From the A/C compressor, route the smooth back side of the belt under the smooth Idler Pulley.
4. Wrap the ribbed side up and around the Alternator.
5. Pull the belt across to the Power Steering Pump (if equipped/applicable, note that some Pentastar platforms use EPS, but follow the accessory path).
6. Route the smooth side of the belt over the Water Pump pulley.
7. Finally, pull the remaining loop down and slide it over the Auto-Tensioner Pulley while holding the tensioner open with your tool.

How to replace the serpentine belt

Replacing the belt on the 2020 ProMaster is a straightforward job if you have the right tools. Due to the tight clearance in the engine bay, standard wrenches might not fit.

Tools required:

• Serpentine belt tool or a low-profile 3/8" drive breaker bar
• Safety glasses and gloves

Step-by-step procedure:

1. Locate the tensioner: The automatic drive belt tensioner is located near the middle-front of the engine accessory drive.
2. Release belt tension: Insert your 3/8" breaker bar or serpentine belt tool into the square receptacle on the tensioner arm. Rotate the tensioner counterclockwise (towards the front of the van) to relieve tension on the belt.
3. Remove the old belt: While holding the tensioner in the released position, slide the belt off the easiest accessible pulley (usually the idler or water pump). Slowly release the tensioner and remove the old belt entirely.
4. Route the new belt: Follow your reference photo and the routing path described above. Loop the belt around all pulleys except the final tensioner or water pump pulley.
5. Install and verify: Rotate the tensioner open again, slip the final loop of the belt into place, and slowly release the tensioner. Double-check every pulley with a flashlight to ensure the belt ribs are perfectly seated in the pulley grooves and the smooth side is flat against the smooth pulleys.

Replacement interval

For the 3.6L Pentastar V6, the serpentine belt should be thoroughly inspected every 20,000 miles. Industry best practices and ASE guidelines recommend replacing the serpentine belt every 60,000 to 90,000 miles, or roughly every 5 years, whichever comes first. EPDM belts (like the ones used on the 2020 ProMaster) don't crack as noticeably as older neoprene belts; instead, the ribs wear down like tire tread.

Signs of a failing belt or tensioner

Don't wait for a breakdown on a delivery route. Watch for these warning signs:

• Squealing or chirping noises: Especially on startup or when the A/C compressor engages. This usually points to a stretched belt or a weak automatic tensioner.
• Visible wear: Look for fraying edges, missing chunks of ribs, or a shiny, glazed appearance on the back of the belt. You can also use a belt wear gauge tool to measure rib depth.
• Accessory issues: A slipping belt can cause heavy steering, dimming headlights, or the A/C blowing warm.
• Tensioner bounce or rattle: While the engine is idling, watch the auto-tensioner. If the arm is bouncing excessively or rattling, the internal spring or dampener is shot, and the tensioner assembly must be replaced immediately.

If you don’t have the time, tools, or space to tackle this job yourself, don’t risk your fleet's reliability. Find a trusted shop on Repairius.