2021 Jeep Wrangler Serpentine Belt: Routing & Part Numbers

The serpentine belt on your 2021 Jeep Wrangler is a single, continuous belt that drives multiple engine accessories, including the alternator, water pump, power steering pump, and A/C compressor. Keeping it in good condition is critical for vehicle reliability. This guide covers the part numbers, routing, and replacement process for the most common engines in the 2021 Wrangler JL.

Note: The 2021 Jeep Wrangler was offered with several engine options, primarily the 3.6L V6 and the 2.0L I-4 Turbo. These engines use different belts, tensioners, and have different belt routings. Always verify parts with your vehicle's VIN before purchasing.

Quick Answer: Parts for Your 2021 Jeep Wrangler

Below are commonly cited part numbers for the 2021 Wrangler's main engine options. Part numbers can vary based on specific options (like eTorque) and build dates, so always confirm compatibility by providing your VIN to a dealership parts department or trusted auto parts store.

For Models with the 3.6L V6 Engine:

• Serpentine Belt Length: Approx. 95.6 inches
• Rib Count: 6
• OEM Mopar Belt PN: 68444229AA
• Aftermarket Cross-References: Gates K060956, Dayco 5060955, Continental 4060955
• Auto-Tensioner Assembly PN: Mopar 68340919AB; Gates 39454
• Idler Pulley PN: Mopar 68155623AA; Gates 36173

For Models with the 2.0L I-4 Turbo Engine:

• Serpentine Belt Length: Approx. 88.2 inches
• Rib Count: 6
• OEM Mopar Belt PN: 68406184AA
• Aftermarket Cross-References: Gates K060882, Dayco 5060880, Continental 4060882
• Auto-Tensioner Assembly PN: Mopar 68403932AA; Gates 39486
• Idler Pulley PN: Mopar 68393847AB; Gates 36802

Belt Routing

Before you remove the old belt, use your phone to take several clear pictures of the belt routing from different angles. This is the most important step for ensuring a smooth installation. The routing path is different for each engine.

3.6L V6 Serpentine Belt Routing

Starting from the main crankshaft pulley at the bottom and moving clockwise:

1. The belt wraps under the Crankshaft pulley.
2. Travels up and around the A/C Compressor pulley.
3. Goes down and around the smooth Idler Pulley.
4. Moves up to the Alternator pulley.
5. Crosses over to the Power Steering Pump pulley.
6. Goes down and around the smooth Water Pump pulley.
7. Finishes by going around the Tensioner pulley before returning to the crank.

2.0L I-4 Turbo Serpentine Belt Routing

Starting from the crankshaft pulley at the bottom and moving clockwise:

1. The belt wraps under the Crankshaft pulley.
2. Travels up and around the smooth Idler Pulley.
3. Goes up to the Alternator pulley.
4. Moves across and down to the A/C Compressor pulley.
5. Finishes by wrapping around the Tensioner before returning to the crank.

How to Replace the Serpentine Belt

Replacing the belt is straightforward with the right tool. You will need a serpentine belt tool or a long-handled 3/8" drive breaker bar.

1. Locate the Auto-Tensioner: Find the automatic tensioner assembly. It's a spring-loaded arm with a pulley on the end. It will have a 3/8" square hole or a hex feature on the body of the arm.
2. Release Tension: Insert your breaker bar or serpentine belt tool into the designated slot on the tensioner. Rotate the tool to move the tensioner arm and release the tension on the belt. The movement is often clockwise on these models.
3. Remove the Old Belt: While holding the tensioner arm with one hand, use your other hand to slip the old belt off a smooth, non-grooved pulley (the idler or water pump pulley is usually easiest).
4. Install the New Belt: Following the photos you took earlier, carefully route the new belt around all the pulleys, saving one easily accessible smooth pulley for last.
5. Secure the New Belt: Apply force to the tensioner tool once more, and slip the belt over the final pulley. Slowly release the tool, allowing the tensioner to apply pressure to the new belt.
6. Final Check: Run your fingers around the entire path, ensuring the belt's ribs are correctly seated in the grooves of every ribbed pulley. An incorrectly seated belt will shred itself almost immediately upon starting the engine.
7. Start the Engine: Start the vehicle and let it run for 15–30 seconds, watching the belt to ensure it is tracking straight and running smoothly.

Replacement Interval

Modern EPDM rubber serpentine belts are very durable. There is no longer a strict mileage interval for replacement. Instead, the belt should be inspected for wear during routine oil changes after 60,000 miles. Plan on a preemptive replacement between 75,000 and 100,000 miles to avoid being stranded by a failed belt.

Signs of a Failing Belt or Tensioner

Listen and look for these warning signs:

• Chirping or Squealing: Sharp squealing noises upon startup, during hard acceleration, or when turning the steering wheel are a classic sign of a worn or slipping belt.
• Visible Wear: Inspect the belt for cracks, fraying edges, missing ribs, or a "glazed" (shiny) appearance on the smooth side.
• Tensioner or Pulley Noise: A rumbling, grinding, or rattling noise from the front of the engine points to a failing bearing in the tensioner or an idler pulley. These should be replaced along with the belt.
• Bouncing Tensioner: If the tensioner arm is visibly vibrating or bouncing while the engine is idling, its internal spring is likely worn out, and it can no longer hold adequate tension.

If you're not comfortable performing this service yourself, Repairius can help.

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