2017 Ford Transit — Serpentine Belt Routing & Length

As an ASE-certified master technician, I’ve worked on countless commercial vehicles, and the 2017 Ford Transit is a frequent visitor to the bay. Whether your Transit is equipped with the 3.7L naturally aspirated V6, the 3.5L EcoBoost V6, or the 3.2L Power Stroke Diesel, keeping the serpentine belt system in top shape is critical for keeping your work van on the road.

Below is your comprehensive reference guide for the 2017 Ford Transit (focusing on the highly common 3.7L and 3.5L V6 gas engines), including belt routing, part numbers, and replacement tips.

Quick Answer: Specifications & Part Numbers (3.5L & 3.7L V6)

Before you begin, always confirm your specific engine option, as the 3.2L diesel utilizes a completely different belt setup. The specs below apply to the main accessory drive belt for the 3.7L and 3.5L gas engines:

• Belt Length: 86.4 inches (varies slightly by manufacturer)
• Rib Count: 6-rib design
• OEM Belt Part Number: Motorcraft JK6-879
• Aftermarket Cross-References: Gates K060864, Dayco 5060865, Continental 4060865
• Auto-Tensioner Part Number: Motorcraft BT-121 (Gates 39316)
• Idler Pulley Part Number: Motorcraft YS-385 (Gates 36334)

Note: The 3.5L/3.7L engines also feature a separate stretch-fit belt for the A/C compressor on some configurations. Always check your exact vehicle's sub-model.

Belt Routing

Since we can't render an image of the belt path here, I highly recommend using your smartphone to take a clear photograph of your existing belt routing before you remove it. It will save you a headache later.

For the main accessory drive on the 3.7L / 3.5L V6, the 6-rib belt routing path generally follows this sequence:

1. Start at the bottom around the ribbed Crankshaft Pulley.
2. Route the belt up and around the A/C Compressor (if on the main drive, otherwise it goes toward the power steering/water pump).
3. Pass the smooth side of the belt under the Idler Pulley.
4. Pull the ribbed side up and over the Alternator.
5. Route down to the Power Steering Pump.
6. Pass the smooth side over the Water Pump.
7. Finally, loop it around the Auto-Tensioner to complete the circuit.

Always ensure that the ribbed side of the belt mates fully with grooved pulleys, and the smooth backside of the belt rides flush against smooth pulleys like the idler and water pump.

How to Replace the Serpentine Belt

Replacing the serpentine belt on a 2017 Ford Transit can be slightly cramped depending on your van's upfit, but it is highly manageable with the right tools.

1. Gather your tools: You will need a dedicated serpentine belt tool or a long 3/8" drive breaker bar.
2. Release the tension: Locate the auto-tensioner on the front of the engine block. Insert your 3/8" breaker bar or belt tool into the square receptacle on the tensioner arm. Rotate the tensioner counter-clockwise (or push it toward the passenger side, depending on your angle) to relieve pressure on the belt.
3. Remove the belt: While holding the tensioner open, slip the belt off the easiest-to-reach smooth pulley (usually the idler or water pump). Carefully release the tensioner arm back to its resting position. Remove the old belt from the engine bay.
4. Install the new belt: Route the new belt following your reference photo or the text guide above. Leave the same smooth pulley for last.
5. Apply tension: Crank the tensioner open again, slip the belt over the final pulley, and release the tensioner.
6. Verify: Double-check every pulley to ensure the ribs are perfectly seated in the grooves. Start the engine and let it run for a minute to ensure the belt tracks straight and true.

Replacement Interval

For commercial applications like the Ford Transit, preventative maintenance is everything. The factory recommended replacement interval for the serpentine belt is typically around 100,000 miles. However, because these vans often idle extensively and carry heavy loads, I highly recommend inspecting the belt every 60,000 to 75,000 miles. If you are replacing the belt, it is industry best practice to replace the automatic tensioner and idler pulley at the same time, as their bearings degrade on a similar timeline.

Signs of a Failing Belt or Tensioner

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

• Squealing or Chirping: High-pitched noises on startup or when turning the steering wheel often indicate a stretched belt or a weak tensioner spring.
• Visible Wear: Look for missing ribs, deep cracking, fraying edges, or a glazed, shiny appearance on the ribbed side of the belt.
• Accessory Failure: If your air conditioning suddenly blows warm, your steering becomes incredibly heavy, or the red battery/alternator warning light turns on, your belt may have snapped or slipped off completely.
• Tensioner Bounce: With the engine running, observe the tensioner. If the arm is bouncing aggressively back and forth, the internal spring has failed and the tensioner assembly must be replaced immediately.

If you aren’t comfortable performing this repair yourself, don't risk a breakdown on the job. Find a trusted shop on Repairius.