2023 Ram 2500 — Transmission & Axle Gear Ratios

Transmission gear ratios

8-speed automatic (ZF 8HP75 behind 6.4L HEMI)

6-speed automatic (68RFE behind 6.7L Cummins)

Available axle ratios

Note: 2023 Ram 2500 rear axles are American Axle (AAM) 11.5-inch units on most configurations. Front axle gearing is matched to the rear on 4x4 trucks.

(Availability can vary by wheelbase/GVWR/package. Always confirm your specific truck’s build sheet.)

How to identify your axle ratio

• Axle tag (Ram/Ford method): Crawl under the rear of the truck and look for the metal tag on a differential cover bolt or stamped on the right/left axle tube. It will list the ratio (e.g., 3.73 or 4.10) and the AAM Bill of Material (BOM) number. The BOM maps to the exact axle build including differential type.
• VIN build sheet (Ram): Enter your VIN on the official Mopar/ramtrucks build sheet site or ask a Ram dealer to print your build sheet. Look for entries like “3.73 Axle Ratio (DMF)” or “4.10 Axle Ratio (DRZ),” and for differential options such as Anti‑Spin (limited‑slip) or electronic lockers (Power Wagon).
• Window sticker: Many window stickers list the axle ratio line item under Mechanical/Performance.
• GM-style RPO stickers (context): GM trucks show axle codes on the door‑jamb RPO label (e.g., GT4, GT5). Ram does not use GM RPOs; use the axle tag or VIN build sheet instead.

Towing vs MPG impact

• Lower number = better highway fuel economy. A 3.73 rear end drops engine RPM at cruise compared with a 4.10, helping mileage and reducing noise—especially when paired with the tall overdrive gears (0.67 in the 8HP75, 0.62 in the 68RFE).
• Higher number = more wheel torque for towing/hauling. A 4.10 multiplies torque ~9.9% more than a 3.73 (4.10 ÷ 3.73), improving launch with heavy trailers, grades, sand, or snow. The trade‑off is higher cruise RPM and slightly lower MPG.
• Transmission interaction: The 8HP75’s deep 1st gear (4.71) already provides strong launch. Gas 6.4L buyers who tow occasionally often find 3.73 perfectly adequate. The 68RFE diesel’s strong low‑RPM torque works well with 3.73; choose 4.10 if you’re near GCWR frequently, in mountainous terrain, or on larger‑than‑stock tires.
• Tire size matters: Upsizing tires effectively “numerically lowers” the final drive. If you run 35s or 37s, a 4.10 can restore factory-like overall gearing and shift performance.

Common issues owners report

• Ring and pinion whine: AAM 11.5 axles can develop coast/load whine if the gear mesh pattern isn’t set correctly after service or if fluid is contaminated. Noise is most apparent 55–70 mph. Quality gear setup and proper 75W‑90/75W‑140 (as specified) help.
• Carrier/pinion bearings: High mileage, frequent heavy towing, or oversize tires increase bearing load, sometimes leading to growl or metal in the oil. Early attention can prevent gear damage.
• Limited‑slip clutch wear (Anti‑Spin): Trucks equipped with clutch‑type limited slip may exhibit chatter on tight turns once friction modifier is depleted. Fluid service with the correct additive typically restores smooth operation.
• Power Wagon lockers: The electronic locker actuators are generally robust; however, water intrusion or infrequent use can cause slow engagement. Cycle lockers periodically and keep breathers clear, especially after deep‑water crossings.

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