2019 Ram 2500 Transmission & Axle Gear Ratios

When it comes to heavy-duty trucks like the 2019 Ram 2500, understanding transmission and axle gear ratios is crucial for optimizing performance, whether you're towing a heavy load or aiming for better fuel economy. These ratios determine how effectively your engine's power is translated to the wheels.

Transmission gear ratios

The 2019 Ram 2500 was offered with two primary transmission options, depending on the engine choice: the 68RFE automatic for the 6.4L HEMI V8 and the Aisin AS69RC automatic for the 6.7L Cummins Turbo Diesel.

68RFE Automatic Transmission (6.4L HEMI V8)

Aisin AS69RC Automatic Transmission (6.7L Cummins Turbo Diesel)

Available axle ratios

The axle ratio plays a significant role in the truck's overall performance, influencing both its towing capabilities and fuel efficiency. For the 2019 Ram 2500, several axle ratios were available.

How to identify your axle ratio

Identifying your Ram 2500's axle ratio is crucial for proper maintenance and upgrades. There are a few reliable methods:

• Door-Jamb RPO Sticker: For Ram trucks, you can often find a build sticker on the driver's side door jamb. Look for a three-digit RPO code that corresponds to the axle ratio. For example, "DMH" typically indicates a 3.73 ratio, and "DMU" indicates a 4.10 ratio.
• Axle Tag: Many axles, particularly on older or heavy-duty trucks, have a metal tag attached to one of the differential cover bolts. This tag will often have the gear ratio stamped directly on it (e.g., "3.73" or "4.10").
• VIN Decoder: A Ram dealership service department or an online VIN decoder service can provide a detailed build sheet for your specific truck, which includes the axle ratio.

Towing vs MPG impact

Axle ratios are a compromise between towing performance and fuel economy. Here's how they generally impact your 2019 Ram 2500:

• Numerically Lower Ratio (e.g., 3.73): A numerically lower axle ratio means the engine turns fewer times for each revolution of the wheels. This results in lower engine RPMs at highway speeds, which generally translates to better fuel economy. However, it also means less mechanical advantage for towing, so while adequate for moderate loads, it might not be ideal for the heaviest trailers.
• Numerically Higher Ratio (e.g., 4.10): Conversely, a numerically higher axle ratio means the engine turns more times for each revolution of the wheels. This provides a greater mechanical advantage, making it easier to get heavy loads moving and maintain speed on inclines. The trade-off is higher engine RPMs at highway speeds, leading to decreased fuel economy.

For the 2019 Ram 2500, if you primarily tow heavy loads frequently, the 4.10 axle ratio would be the more suitable choice to maximize towing capacity and reduce strain on the powertrain. If your usage involves more empty highway driving or lighter towing, the 3.73 ratio will offer better fuel efficiency.

Common issues

While Ram's drivelines are generally robust, some common issues can arise with differential components over time and use:

• Ring and Pinion Whine: A persistent whining noise that changes with vehicle speed and load can indicate wear or improper setup of the ring and pinion gears within the differential. This often becomes more noticeable at certain speeds or when accelerating/decelerating.
• Carrier Bearing Wear: The carrier bearings support the differential carrier. Worn carrier bearings can lead to clunking, humming, or howling noises, particularly when turning or under acceleration. If left unaddressed, this can lead to further damage to the differential.
• Limited-Slip Clutch Pack Wear: If your Ram 2500 is equipped with a limited-slip differential, the clutch packs can wear out over time. Symptoms of worn clutches include a chattering or binding sensation when making turns at low speeds, particularly noticeable during parking maneuvers.

Regular differential fluid changes using the correct fluid type (including friction modifier for limited-slip units) are crucial for extending the life of these components.

Find a driveline shop on Repairius.