2021 Ram ProMaster Transmission & Axle Gear Ratios

Transmission gear ratios

The 2021 Ram ProMaster is equipped with a robust 6-speed automatic transmission designed to handle the demands of commercial use. This transmission, paired with the powerful 3.6L Pentastar V6 engine, offers a wide range of gear ratios to optimize performance for various applications.

Available axle ratios

The 2021 Ram ProMaster offers a selection of axle ratios to cater to different needs, balancing between towing capability and fuel efficiency. The availability of these ratios can depend on the specific trim level, wheelbase, and other optional packages.

How to identify your axle ratio

Identifying your Ram ProMaster's axle ratio is crucial for proper maintenance and modifications. For the 2021 Ram ProMaster, the easiest way to identify the axle ratio is by checking the build sticker or RPO (Regular Production Option) codes. For Ram vehicles, this sticker is typically located on the underside of the hood, inside the glovebox, or can sometimes be found on the driver's side door jamb. Look for a three-digit code that starts with "D" for axle ratios. Common codes for the ProMaster include DFA (3.86) and DFG (4.07). If you cannot find the sticker, a Ram dealership can provide this information using your VIN.

Towing vs MPG impact

Numerically Lower Ratio (e.g., 3.86): A numerically lower axle ratio means the engine will spin at lower RPMs at a given road speed. This generally translates to better fuel economy, especially during highway driving. However, it also means less mechanical advantage for acceleration and towing, making it less suitable for consistently hauling heavy loads.

Numerically Higher Ratio (e.g., 4.07): A numerically higher axle ratio allows the engine to rev higher at a given road speed. This provides more torque to the wheels, significantly improving towing capacity, acceleration, and performance when carrying heavy cargo. The trade-off is often a reduction in fuel economy, particularly at highway speeds, as the engine works harder.

For the 2021 Ram ProMaster, the 3.86 ratio provides a good balance for general hauling and city driving, offering reasonable fuel efficiency. The 4.07 ratio is ideal for those who frequently tow heavy trailers or operate their ProMaster with maximum payloads, prioritizing power and capability over marginal fuel economy gains.

Common issues

While the Ram ProMaster's drivetrain is generally robust, some common issues can arise related to the axle and differential, especially in high-mileage or heavily utilized vehicles:

• Ring and Pinion Whine: A high-pitched whine that changes with vehicle speed (not engine RPM) can indicate wear or improper setup of the ring and pinion gears within the differential. This often becomes more noticeable during acceleration or deceleration.
• Carrier Bearing Wear: The carrier bearings support the differential carrier. If these bearings wear out, they can produce a growling or rumbling noise that may increase with vehicle speed or when cornering. Severe wear can lead to differential failure.
• Limited-Slip Clutch Wear (if equipped): Some ProMasters may come with an optional limited-slip differential. Over time, the clutch packs within these differentials can wear, leading to a loss of limited-slip function, noticeable as one wheel spinning freely in low-traction situations where both should be driving. Squealing or chattering noises during turns can also indicate worn clutches.

Regular differential fluid changes with the correct fluid type (including friction modifier if a limited-slip differential is present) are crucial for prolonging the life of these components.

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