2018 Ram 3500 Transmission & Axle Gear Ratios

Transmission gear ratios

The 2018 Ram 3500 offered two robust transmission options to handle its impressive capabilities: the 68RFE 6-speed automatic and the Aisin AS69RC 6-speed automatic. Each is designed to deliver power efficiently, whether you're towing heavy loads or cruising on the highway.

68RFE 6-Speed Automatic

Aisin AS69RC 6-Speed Automatic

Available axle ratios

The 2018 Ram 3500 provided a range of axle ratios to optimize for various tasks, from heavy-duty towing to more balanced performance.

How to identify your axle ratio

Identifying your Ram 3500's axle ratio is crucial for understanding its performance characteristics. For Ram trucks, the most reliable way to find this information is through the build sticker or by checking the axle tag itself.

1. Door-Jamb RPO Sticker: Open your driver's side door and look for a white sticker on the door jamb. This sticker contains various Regular Production Option (RPO) codes. Look for a three-digit code starting with "DM" (e.g., DM7, DME, DMG). This code will correspond to your installed axle ratio.

2. Axle Tag: For an older vehicle or if the sticker is missing/unreadable, you might find a metal tag attached to one of the differential cover bolts on the rear axle. This tag will often have the ratio stamped directly on it (e.g., "3.73"). Be aware that these tags can become corroded or missing over time.

3. VIN Decoder: Many online VIN decoders can provide your vehicle's original build sheet information, which will include the axle ratio. This is a good option if the physical tags are absent.

Towing vs MPG impact

Your axle ratio plays a significant role in how your 2018 Ram 3500 performs, particularly concerning towing capability and fuel economy.

• Numerically Lower Ratio (e.g., 3.42): A lower numerical ratio means the engine turns fewer times for each rotation of the wheels. This results in lower RPMs at highway speeds, leading to better fuel economy. However, it also means less mechanical advantage for accelerating and towing heavy loads. While still capable, trucks with lower ratios are generally "best for" fuel economy-conscious owners or those who tow lighter loads less frequently.

• Numerically Higher Ratio (e.g., 4.10): A higher numerical ratio means the engine turns more times for each wheel rotation. This provides greater mechanical advantage, resulting in superior towing and hauling capability and better acceleration, especially from a standstill. The trade-off is higher engine RPMs at cruising speeds, which translates to lower fuel economy. Trucks with higher ratios are ideal for owners who regularly tow heavy trailers or operate in demanding conditions.

• Balanced Ratio (e.g., 3.73): This ratio strikes a good balance between towing performance and fuel efficiency, making it a popular choice for all-around use. It provides adequate towing capability for most needs without significantly sacrificing fuel economy.

Common issues

While Ram 3500 drivetrains are generally very robust, some common issues can arise with differential components over time and use:

• Ring & Pinion Whine: A persistent whining noise that changes with vehicle speed or acceleration often indicates wear or improper setup of the ring and pinion gears within the differential. This can be caused by inadequate lubrication, heavy towing, or improper installation after a service.

• Carrier Bearing Wear: The carrier bearings support the differential carrier. If these bearings wear out, they can produce a rumbling or growling noise, especially noticeable during turns or acceleration. Severe wear can lead to excessive play and potential damage to other differential components.

• Limited-Slip Clutch Wear (if equipped): Trucks with a limited-slip differential use clutch packs to help distribute power between the wheels. Over time, these clutch packs can wear out, leading to a loss of the limited-slip function, noticeable as one wheel slipping excessively or chattering when turning at low speeds. Regular fluid changes with the correct friction modifiers are essential for longevity.

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