2021 Toyota Tundra Serpentine Belt Routing, Length & Part Numbers

As an ASE-certified master technician, I know that maintaining the drive belt system on a heavy-duty truck is critical to keeping it on the road. The 2021 Toyota Tundra, equipped primarily with the legendary 5.7L 3UR-FE V8 engine, relies on a single, heavy-duty serpentine belt to drive all its engine accessories. Whether you are performing routine maintenance or dealing with a squealing tensioner, having the right part numbers and routing information makes all the difference.

Below is your comprehensive guide to the 2021 Toyota Tundra serpentine belt system, including routing instructions, lengths, and exact part numbers.

Quick answer

For the 2021 Toyota Tundra (5.7L V8):

• Belt Length: 94.8 inches (2410 mm)
• Rib Count: 8-rib
• OEM Belt Part Number: Toyota 90916-A2015 (or 90916-02680)
• Aftermarket Cross-References: Gates K080948, Dayco 5080948, Continental Elite 4080948, Bando 8PK2410
• Auto-Tensioner Part Number: Toyota OEM 16620-0S012 (Aftermarket: Gates 39228)
• Idler Pulley Part Number: Toyota OEM 16604-0S010 (Aftermarket: Gates 36173)

Note: Always verify your specific engine option and trim with your parts supplier, though the 5.7L V8 was the standard powertrain for the 2021 model year.

Belt routing

Because the 2021 Tundra uses a long 8-rib belt to drive multiple high-draw accessories, getting the routing exactly right is mandatory. Pro Tip: Always use your smartphone to take a clear photograph of the existing belt's routing path before you remove it.

If your belt has already snapped or been removed, follow this text-based step-by-step routing path:

1. Start by looping the belt around the bottom of the Crankshaft pulley (the largest pulley at the bottom center of the engine).
2. Route the belt down and around the A/C compressor on the lower passenger side.
3. Bring the belt up from the A/C compressor and over the smooth Idler pulley.
4. Run it across to the driver's side and around the Alternator.
5. Route it down around the Power steering pump pulley.
6. Bring it back toward the center and over the large Water pump pulley.
7. Finally, pull the remaining slack over the Auto-tensioner pulley to complete the circuit.

Make sure the ribbed side of the belt sits perfectly in the grooves of all the ribbed pulleys, while the smooth back side of the belt rides cleanly on the smooth idler and tensioner pulleys.

How to replace the serpentine belt

Replacing the belt on the 5.7L V8 requires basic hand tools but a bit of leverage due to the heavy-duty tensioner spring.

1. Locate the tensioner: The auto-tensioner is located near the center-bottom of the engine accessory drive. It features a 14mm hex bolt on the pulley.
2. Relieve tension: Using a long-handled 14mm wrench or a specialized serpentine belt tool, rotate the tensioner counter-clockwise (toward the driver's side) to compress the internal spring and relieve tension on the belt.
3. Slip the belt off: While holding the tensioner back, carefully slip the old belt off the easiest accessible pulley (usually the alternator or water pump). Slowly release the tensioner back to its resting position.
4. Route the new belt: Route your new 8-rib belt according to the path described in the "Belt routing" section above, leaving the tensioner for last.
5. Install the new belt: Compress the tensioner again, slip the final loop of the belt over the tensioner pulley, and gently release the tensioner.
6. Verify: Double-check every pulley to ensure the belt ribs are fully seated in the grooves. Start the engine and observe the belt to ensure it tracks smoothly without jumping or squeaking.

Replacement interval

For the 2021 Toyota Tundra, the serpentine belt should be thoroughly inspected every 30,000 miles or 3 years. Modern belts are made from EPDM (ethylene propylene diene monomer) rubber, which doesn't crack as noticeably as older neoprene belts. Instead, they wear out like tire tread.

A good rule of thumb is to replace the serpentine belt every 60,000 to 90,000 miles. I highly recommend replacing the auto-tensioner and idler pulley at the same time (usually around the 100k-mile mark), as the bearings in these components have a similar lifespan to the belt itself.

Signs of a failing belt or tensioner

Don't wait until you're stranded with no power steering and an overheating engine. Watch out for these warning signs:

• Squealing or Chirping: A high-pitched noise, especially on startup or when accelerating, indicates belt slip. This is often caused by a stretched belt or a weak auto-tensioner spring.
• Visible Wear: Look for missing chunks of rubber, fraying edges, or a shiny, glazed appearance on the ribbed side of the belt. You can also use a belt wear gauge to check groove depth.
• Accessory Malfunctions: Heavy steering, a battery warning light (due to the alternator not spinning fast enough), or poor A/C performance can all point to a slipping drive belt.
• Pulley Wobble or Noise: If you hear a low rumble, grinding, or see the tensioner arm bouncing aggressively while the engine runs, the tensioner or idler pulley bearings are failing.

If you aren't comfortable tackling this heavy-duty belt replacement on your own, don't risk a breakdown. Find a trusted shop on Repairius.