2017 Ram 2500: Transmission & Axle Gear Ratios Guide

The 2017 Ram 2500 is a heavy-duty workhorse renowned for its robust powertrain options, including the legendary 6.7L Cummins Turbo Diesel and the powerful 5.7L and 6.4L HEMI V8 engines. To effectively harness this power for towing, hauling, or highway cruising, Ram paired these engines with specific transmissions and axle ratios. Understanding these gear ratios is crucial for heavy-duty truck owners who want to optimize their vehicle for specific tasks.

Below is a comprehensive guide to the transmission and axle gear ratios for the 2017 Ram 2500.

Transmission gear ratios

The 2017 Ram 2500 was offered with three primary transmissions: the 66RFE 6-speed automatic (for gas engines), the 68RFE 6-speed automatic (for the 6.7L Cummins), and the G56 6-speed manual (exclusive to the Cummins).

66RFE & 68RFE 6-Speed Automatic Transmissions

Both the 66RFE (paired with HEMI V8s) and the 68RFE (paired with the Cummins) share the same internal gear ratios, though the 68RFE features significantly beefed-up internals to handle the diesel's massive torque output.

G56 6-Speed Manual Transmission

Available exclusively with the 6.7L Cummins Turbo Diesel, the G56 is a heavy-duty manual transmission favored by purists for its direct control over the powerband.

Available axle ratios

The final drive ratio in your differential dictates how engine power is translated to the wheels. The 2017 Ram 2500 offered three main axle ratios, depending on the engine configuration.

Note: For the 2017 model year, Ram 2500 trucks equipped with the 6.7L Cummins were exclusively available with the 3.42 axle ratio from the factory to meet emissions and fuel economy targets, relying on the immense low-end torque of the diesel to handle heavy loads.

How to identify your axle ratio

If you are unsure which gear ratio your 2017 Ram 2500 is equipped with, there are a few simple ways to find out:

1. The Axle Tag: Crawl under the rear of your truck and look at the differential cover. Ram (Chrysler/FCA) typically bolts a small metal identification tag to one of the differential cover bolts. This tag will have the ratio stamped directly into it (e.g., "3.73" or "4.10").
2. The Equipment Listing (Glovebox / Door Jamb): Check the glovebox or the driver’s side door jamb for the vehicle equipment listing or RPO sticker. Look for the three-digit codes listed in the table above (DMX, DME, or DMF).
3. VIN Decoder or Build Sheet: The most foolproof method is to run your Vehicle Identification Number (VIN) through a Chrysler/Ram build sheet portal or a reputable online VIN decoder. This will generate a factory build sheet listing the exact axles and ratios installed on the assembly line.

Towing vs MPG impact

The relationship between your axle ratio, fuel economy, and towing capability is a balancing act of leverage.

Numerically Lower Ratios (e.g., 3.42): A lower number means the driveshaft turns fewer times for every full rotation of the tires. This keeps engine RPMs lower at highway speeds, resulting in better fuel economy and reduced engine noise. However, it provides less mechanical leverage, meaning the engine has to work harder to get a heavy load moving from a dead stop. This is why the 3.42 is standard on the Cummins—the diesel engine has enough raw torque to overcome the lack of gear leverage.

Numerically Higher Ratios (e.g., 4.10): A higher number provides maximum mechanical advantage. The engine turns at a higher RPM at highway speeds, which negatively impacts fuel economy (often dropping MPG by 1-2 points). However, this leverage makes it incredibly easy to pull heavy trailers up steep grades or accelerate from a stop with a full payload. For a gas-powered 6.4L HEMI tasked with heavy fifth-wheel towing, the 4.10 ratio is highly recommended.

Common issues

While the heavy-duty drivelines in the 2017 Ram 2500 are generally very robust, they are subjected to immense stress and can develop issues over time, especially if the truck is frequently used for maximum-capacity towing.

• Ring & Pinion Whine: A high-pitched whining noise from the rear end during acceleration or deceleration often points to wear on the ring and pinion gears, or improper backlash caused by worn bearings.
• Carrier Bearing Wear: The heavy two-piece driveshafts on Crew Cab and Mega Cab models utilize a center support (carrier) bearing. If this bearing fails, you will feel a distinct vibration under the floorboards upon acceleration.
• Limited-Slip Clutch Wear: For trucks equipped with the Anti-Spin rear differential (Code DSA), the internal clutch packs can wear out over time. If you notice wheel hop, chattering around tight corners, or a loss of traction on slippery boat ramps, the differential clutches may require replacement or friction modifier additive.

Find a driveline shop on Repairius. If you need a differential fluid service, an axle rebuild, or a gear ratio swap to better suit your towing needs, use Repairius.com to find a certified heavy-duty driveline specialist in your area.