2022 Kenworth T680 Serpentine Belt Routing & Length

Heavy-duty trucks like the 2022 Kenworth T680 require absolute reliability, and the serpentine belt is the literal lifeline for your engine's vital accessories. Whether your T680 is powered by the standard PACCAR MX-13 or the Cummins X15, maintaining the accessory drive system is critical to preventing costly downtime.

As an ASE-certified master technician, I always advise fleet managers and owner-operators to keep a spare belt and tensioner in the side box. Below is the essential reference guide for the main drive serpentine belt on a 2022 Kenworth T680 (focused on the common PACCAR MX-13 engine configuration).

Note: Heavy-duty truck configurations vary greatly based on APUs, dual alternators, and specific engine options. Always verify part numbers against your specific Engine Serial Number (ESN) or VIN.

Quick answer

• Rib count: 8-rib (Standard heavy-duty main drive)
• Belt length: Approximately 81.4 inches (varies slightly by alternator package)
• OEM belt PN: PACCAR 2137953 (MX-13 primary drive)
• Aftermarket cross-references: Gates FleetRunner K080814HD, Dayco 5080814, Continental Elite 4080814
• Auto-tensioner PN: PACCAR 1941656 (Gates 38667)
• Idler pulley PN: PACCAR 1900350

Belt routing

Because engine bays are tight and routing diagrams can sometimes wear off the radiator shroud, we highly recommend using your smartphone to photograph the existing belt's path before you remove it.

For the standard MX-13 accessory drive, the routing path generally follows this text-based step-by-step description (smooth side of the belt rides on smooth pulleys; ribbed side on grooved pulleys):

1. Start by looping the belt down around the bottom of the Crankshaft pulley (ribbed).
2. Route it up and over the A/C compressor (ribbed).
3. Bring the back (smooth) side of the belt under the Idler pulley.
4. Pull it up and over the Alternator pulley (ribbed).
5. Route it down around the Power steering pump (ribbed).
6. Bring it across to the Water pump (smooth or ribbed depending on exact ESN, usually ribbed on primary drive).
7. Finally, slip the belt under the Auto-tensioner pulley (smooth).

How to replace the serpentine belt

Working on a Class 8 truck means dealing with heavy-duty components with high spring rates.

1. Safety first: Ensure the truck is parked on level ground, engine off, keys removed from the ignition, and wheels chocked.
2. Locate the tensioner: Find the automatic belt tensioner situated near the center/lower-right of the accessory drive.
3. Relieve tension: Insert a 1/2-inch drive heavy-duty serpentine belt tool or a long 1/2-inch breaker bar (note: while automotive tensioners often use 3/8", heavy-duty truck tensioners typically require a 1/2" drive or a specific socket size) into the tensioner's square receiver or onto the pulley bolt. Rotate the tensioner away from the belt to release the pressure.
4. Remove the belt: Slide the old belt off the easiest to reach pulley (usually the alternator or water pump). Slowly release the tensioner back to its resting position.
5. Inspect components: Spin the idler and tensioner pulleys by hand. They should spin smoothly with no wobble, grinding, or fretting.
6. Install the new belt: Route the new belt following the path described above (or your reference photo). Leave the tensioner pulley for last.
7. Engage tensioner: Rotate the tensioner again, slip the belt over the final pulley, and carefully release the tensioner to apply pressure. Double-check that all ribs are properly seated in the pulley grooves.

Replacement interval

For commercial over-the-road trucks like the T680, preventative maintenance is key. The serpentine belt should be thoroughly inspected during every standard PM service. Most fleets replace the main drive belts every 100,000 miles or 12 months, whichever comes first. Heavy-duty belts endure extreme heat, dust, and continuous hours of operation, making them prone to wear much faster than passenger vehicle belts. We recommend replacing the auto-tensioner and idler pulleys every second belt change (approx. 200,000 miles) to prevent bearing failures on the road.

Signs of a failing belt or tensioner

Don't wait for a breakdown to replace your belt. Look out for these warning signs:

• Squealing or chirping: Often heard at startup or under heavy electrical load, indicating a glazed belt or a weak tensioner spring.
• Visual wear: Look for missing ribs, cracks across the ribs (more than 3 cracks per inch is a failure), fraying edges, or chunking.
• Loss of accessories: A sudden heavy feel in the steering wheel (loss of power steering), the alternator charging light coming on, or a sudden loss of cab A/C.
• Tensioner bounce: While the engine is idling, watch the tensioner arm. If it bounces excessively or vibrates violently, the internal dampener is shot and the tensioner assembly must be replaced.

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