2018 Ram ProMaster Transmission & Axle Gear Ratios

Transmission gear ratios

The 2018 Ram ProMaster comes with a single transmission option across all its configurations, a proven 6-speed automatic that offers a good balance of durability and efficiency for commercial use.

62TE 6-Speed Automatic Transmission

Available axle ratios

The axle ratio plays a significant role in how your ProMaster performs, influencing both its towing capabilities and fuel efficiency. Ram offers a few options to best suit different needs. The axle ratio is often tied to the specific ProMaster model (1500, 2500, 3500) and engine choice, as well as optional packages.

2018 Ram ProMaster Axle Ratios

Note: The 3.86 axle ratio is standard on most 2018 ProMaster models equipped with the 3.6L V6 engine, offering a good all-around performance. The 4.08 ratio is a more aggressive option, aimed at maximizing towing capacity, often found in heavy-duty configurations or specific towing packages.

How to identify your axle ratio

Identifying your ProMaster's axle ratio is crucial for proper maintenance, part replacement, or assessing its capabilities. For Ram vehicles, you typically won't find a specific "axle tag" like some other manufacturers. Instead, you'll rely on the RPO (Regular Production Option) sticker or a VIN decoder.

RPO Sticker: Look for a sticker on the inside of your driver's side door jamb. This sticker contains a wealth of alphanumeric codes representing all the options and features installed on your vehicle from the factory. Find the three-character RPO codes for the axle ratio, as listed in the table above (e.g., NHE for 3.86, NHM for 4.08).

VIN Decoder: Many online VIN decoder websites can provide a detailed breakdown of your vehicle's specifications, including the axle ratio, by simply entering your 17-digit Vehicle Identification Number.

Towing vs MPG impact

The axle ratio has a direct and inverse relationship with both towing capability and fuel economy:

• Numerically Higher Ratio (e.g., 4.08): This ratio means the engine will spin more revolutions for every rotation of the wheels. This provides more torque to the wheels, which is excellent for towing heavy loads, hauling, and accelerating from a stop. The downside is that at highway speeds, the engine will be revving higher, leading to lower fuel efficiency (MPG).
• Numerically Lower Ratio (e.g., 3.86): Conversely, a lower ratio means the engine spins fewer times for each wheel rotation. This results in better fuel economy at cruising speeds as the engine is operating at lower RPMs. However, it will reduce the available torque at the wheels, making it less ideal for heavy towing or frequent starts with heavy loads.

Choosing the right axle ratio depends on your primary use for the ProMaster. If you regularly haul heavy equipment or tow significant loads, the higher ratio will be beneficial despite a slight fuel economy penalty. If your ProMaster is primarily used for lighter cargo and highway driving, the lower ratio will help save on fuel costs.

Common issues

The Ram ProMaster's drivetrain is generally robust, but like any mechanical system, certain components can experience wear or issues over time, especially in high-mileage commercial applications.

• Differential Noise (Whine/Hum): A common complaint can be a noticeable whine or hum coming from the rear axle, particularly at certain speeds or under acceleration/deceleration. This can indicate wear in the ring and pinion gears, bearings, or improper backlash. Ignoring such noises can lead to more severe damage.
• Carrier Bearing Wear: While not always a specific ProMaster issue, carrier bearings (which support the driveshaft) can wear out, leading to vibrations, clunking noises, or driveline play. This is more prevalent in vehicles constantly carrying heavy loads or experiencing rough roads.
• Limited-Slip Differential Clutch Wear (if equipped): If your ProMaster is equipped with an optional limited-slip differential, the clutch packs within can wear down over time. This can result in a loss of limited-slip function (one wheel spinning freely) and sometimes groaning or chattering noises during turns. Regular fluid changes with the correct friction modifier are crucial for these units.

Regular inspection of fluid levels and conditions, adherence to maintenance schedules, and addressing any unusual noises promptly can help mitigate these issues and prolong the life of your ProMaster's drivetrain.

Find a driveline shop on Repairius.