2015 Ram ProMaster Transmission & Axle Gear Ratios

Transmission gear ratios

The 2015 Ram ProMaster comes with a robust 6-speed automatic transmission designed to handle the demands of a commercial van. There are two primary transmission options, each paired with a specific engine.

62TE 6-Speed Automatic (3.6L Pentastar V6)

AISIN AS68RC 6-Speed Automatic (3.0L EcoDiesel I4)

Available axle ratios

The 2015 Ram ProMaster offers a range of axle ratios to optimize for either towing capability or fuel economy, depending on the application and engine choice.

Note: Ram ProMaster vans often simplify axle ratio offerings, with the standard ratio being the most common. Specific special order or heavy-duty packages might offer variations, but for 2015, the 3.86 ratio was widely standard across both engine options.

How to identify your axle ratio

Identifying your Ram ProMaster's axle ratio is crucial for proper maintenance and modifications. Unlike some other manufacturers, Ram (and the broader Chrysler/Fiat/Dodge family) doesn't always have a distinct RPO sticker on the door jamb that explicitly lists axle ratios with a unique code like GM. However, here are the most common methods:

• VIN Decoder: The most reliable method is often a VIN decoder service. Many online resources and dealer service departments can provide a detailed build sheet for your specific VIN, which will list all installed options, including the axle ratio.
• Underhood Emissions Sticker: Some Ram vehicles may have a sticker under the hood that lists key powertrain specifications, including the axle ratio. This is not universal, but worth checking.
• Dealer Service Department: Provide your VIN to any Ram dealership's service department. They can access your vehicle's build sheet and tell you the exact axle ratio it came with from the factory.
• Physical Inspection (Less Common for ProMaster): In some vehicles, an axle tag is affixed to one of the differential cover bolts. For the ProMaster, this is less common for ratio identification, but it's always a good habit to visually inspect your differential for any stamped or stick-on tags.

Towing vs MPG impact

Your axle ratio plays a significant role in determining your Ram ProMaster's performance characteristics, specifically influencing towing capability and fuel economy:

• Numerically Lower Ratio (e.g., hypothetical 3.55): While not a primary option for the ProMaster, a numerically lower ratio would mean the engine runs at lower RPMs at a given road speed. This generally leads to better fuel economy on the highway and a quieter ride. However, it results in reduced towing capacity and slower acceleration, as the engine has less mechanical advantage.

• Numerically Higher Ratio (e.g., 3.86): The 3.86 ratio offered in the 2015 ProMaster provides a good balance. A numerically higher ratio means the engine runs at higher RPMs for a given road speed. This provides greater torque multiplication to the wheels, resulting in improved towing capacity and quicker acceleration (especially from a stop). The trade-off is slightly lower fuel economy, particularly at highway speeds, and potentially more engine noise.

For the 2015 ProMaster, the 3.86 axle ratio was chosen as a versatile option to accommodate the varied cargo and towing needs of a commercial van, providing a solid blend of capability without severely impacting fuel efficiency.

Common issues

While the Ram ProMaster is generally a reliable workhorse, like any vehicle with a driveline, certain components can experience wear over time.

• Ring and Pinion Whine: A common symptom of worn or improperly set-up differential gears is a whining noise that changes with road speed and load. This can indicate worn gear teeth or improper backlash, often requiring a professional differential rebuild.
• Carrier Bearing Wear: The bearings that support the differential carrier can wear out, leading to a rumble or growl that is often heard from the rear of the vehicle. This noise typically changes pitch when turning or under different loads.
• Limited-Slip Clutch Wear (if equipped): If your ProMaster is equipped with a limited-slip differential, the internal clutches can wear over time, leading to a loss of traction in slippery conditions, or sometimes chattering/binding noises during turns. Regular fluid changes with the correct friction modifier are essential for preserving the life of these units.

Maintaining proper differential fluid levels and using the correct specification of fluid are paramount to the longevity of your ProMaster's axle assembly. Any unusual noises or vibrations from the driveline should be investigated promptly by a qualified technician.

Find a driveline shop on Repairius.