The 6.7 Cummins uses a single serpentine belt that drives the alternator, power steering pump, water pump, and air conditioning compressor off the crankshaft pulley. The exact path can vary slightly by year and accessory package, so always verify with the factory belt diagram on the radiator support or in the service manual.
Overview of the serpentine belt system
The ISB 6.7L engine relies on one continuous belt with an automatic tensioner and a pair of idlers to guide it around all four accessories. Proper routing keeps the belt aligned with each pulley groove and prevents premature wear or detachment as the engine runs. If the belt is misrouted, it can slip, squeal, or fail to drive critical components such as the water pump or alternator.
Typical routing for most Ram 6.7 Cummins engines
Below is a common serpentine-belt sequence used on the ISB 6.7L in Ram 2500/3500 trucks. If your vehicle has a different accessory layout, the order or wrap may vary slightly.
- Crankshaft pulley to the upper idler/tensioner
- From the upper idler/tensioner to the alternator
- From the alternator to the power steering pump
- From the power steering pump to the water pump
- From the water pump to the A/C compressor
- From the A/C compressor to the lower idler and back to the crankshaft pulley
Note: Some installations route the belt in a slightly different sequence depending on the exact A/C compressor, P/S pump mounting, or optional equipment. The direction of wrap and the exact idler positions can differ by year or configuration. Always verify with the diagram under the hood.
Year-to-year variations and where to find the diagram
How to locate the correct diagram
Factory belt diagrams are the most reliable reference. Look for a belt routing sticker on the radiator support or the inner fender area. If the sticker is missing, consult the vehicle’s service manual for your exact year and accessory package to confirm the correct path.
Practical tips for replacement and maintenance
If you’re replacing the belt yourself, follow the exact routing shown in your diagram, note the belt length and groove width, and use the proper tension according to the service manual. After installation, rotate the engine by hand to ensure the belt seats correctly on all pulleys before starting the truck. Listen for unusual squeaks or slipping and recheck tension after a short test drive.
Wrap-up and safety tips
Correct belt routing is essential to keep the alternator charging, coolant circulating, and power steering functioning smoothly. A misrouted belt can cause loss of electrical power, overheating, or steering issues. When in doubt, consult the official diagram for your exact year and accessory configuration and consider having a professional perform the replacement if you’re unsure about the routing.
Summary
In short, the 6.7 Cummins relies on a single serpentine belt that travels around the crank pulley and four accessories (alternator, power steering pump, water pump, and A/C compressor) via a fixed set of pulleys and idlers. While a common routing covers most Ram trucks, always verify your specific year and equipment with the factory diagram to ensure a correct installation.