2018 Ram 1500 Transmission & Axle Gear Ratios

Transmission gear ratios

The 2018 Ram 1500 was available with several transmission options, primarily the 8-speed automatic. Here are the internal gear ratios for each:

ZF 8HP70 8-Speed Automatic (Standard on most V8 models, optional on some V6 models)

ZF 8HP75 8-Speed Automatic (Often found with higher GVWR and Hemi)

TorqueFlite 8 (845RE) 8-Speed Automatic (Common with 3.6L Pentastar V6)

Available axle ratios

The 2018 Ram 1500 offered a range of axle ratios to suit various needs, from fuel economy to heavy towing. These ratios often varied based on engine, trim level, and specific option packages.

Note: The codes "DMG", "DMH", "DMJ", "DML", "DMM", "DMN" are internal Chrysler (Ram) option codes that often indicate the axle ratio. These are not always explicit RPO codes found directly on the door jamb sticker but are used internally for build sheets and service information.

How to identify your axle ratio

Identifying your Ram 1500's axle ratio can be done in a few ways:

• Door-Jamb RPO Sticker: For GM vehicles, this is the primary method, but for Ram, it's less common to find an explicit axle ratio code here. You might find a generic axle code, but it usually doesn't specify the ratio directly. Instead, look for a "build sheet" or "equipment list" sticker, sometimes located in the glove box or under the hood, which may have more detailed RPO codes.
• Axle Tag: Many Ram 1500s will have a metal tag attached to one of the differential cover bolts. This tag typically contains stamped information including the gear ratio (e.g., "3.55"). It might also have codes for the differential type (e.g., limited-slip, open).
• VIN Decoder: Using a Mopar or reputable third-party VIN decoder online can often pull up the original build sheet information for your specific truck, which will list the factory-installed axle ratio.
• Counting Teeth (Last Resort): If all else fails, you can remove the differential cover and count the teeth on the ring gear and the pinion gear. Divide the ring gear teeth by the pinion gear teeth to get your ratio. This is a more involved method and usually unnecessary.

Towing vs MPG impact

Your axle ratio plays a significant role in how your truck performs in terms of towing capability and fuel economy:

• Numerically Lower Ratio (e.g., 3.21): This means the driveshaft turns fewer times for each rotation of the wheels. This setup provides lower engine RPMs at highway speeds, resulting in better fuel economy. However, it also means less torque multiplication to the wheels, reducing towing capacity and acceleration.
• Numerically Higher Ratio (e.g., 3.92): With a higher ratio, the driveshaft turns more times for each wheel rotation. This increases torque multiplication, providing better acceleration and significantly enhancing towing and hauling capabilities. The trade-off is higher engine RPMs at cruising speeds, leading to decreased fuel economy.
• Balanced Ratio (e.g., 3.55): This ratio offers a good compromise between towing performance and fuel efficiency, making it a popular choice for those with varied needs.

When choosing or identifying your axle ratio, consider your primary use case. If you tow heavy loads frequently, a higher ratio is beneficial. If your truck is mainly a daily driver with occasional light hauling, a lower ratio will save you money at the pump.

Common issues

The axle and differential components of the 2018 Ram 1500 are generally robust, but some common issues can arise over time:

• Ring & Pinion Whine: A persistent howling or whining noise, especially when accelerating or decelerating, can indicate wear or improper setup of the ring and pinion gears. This is often due to improper backlash or bearing wear.
• Carrier Bearing Wear: The bearings supporting the differential carrier can wear out, leading to growling noises, vibration, or even fluid leaks. This is often more noticeable during turns or changes in speed.
• Limited-Slip Clutch Wear: If your Ram is equipped with a limited-slip differential, the internal clutches can wear out over time. Symptoms include a loss of traction in slippery conditions (where one wheel spins freely), chatter or binding during turns, or a general reduction in the effectiveness of the limited-slip feature.
• Differential Fluid Leaks: Leaks can occur around the differential cover gasket, pinion seal, or axle seals. Regularly checking your differential fluid level is crucial to prevent premature wear due to low lubrication.

Regular maintenance, including differential fluid changes as recommended by Ram, can help prevent many of these issues and extend the life of your drivetrain components.

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