2023 Ram 1500 — Transmission & Axle Gear Ratios

Transmission gear ratios

TorqueFlite 850RE (ZF 8HP50-based) — 3.6L Pentastar eTorque

TorqueFlite 8HP75 — 5.7L HEMI (incl. eTorque) and 3.0L EcoDiesel

TorqueFlite 8HP95 — TRX 6.2L Supercharged HEMI

Available axle ratios

Notes:

• Anti-Spin limited-slip differential (LSD) is commonly packaged; Mopar sales code often shown as DSA (Anti-Spin Differential Rear Axle).
• The 1500 (DT) lineup does not typically offer 4.10+ ratios from the factory; those are more common on HD (2500/3500) trucks.

How to identify your axle ratio

• Ram-specific methods
  • Axle tag: Look for a small metal tag or sticker on the rear differential cover or axle tube. It will list the ring-and-pinion ratio (e.g., 3.55) and sometimes a part number. Clean the area to read it clearly.
  • Build sheet via VIN: Enter your VIN on Mopar’s official build-sheet lookup (or ask a Ram dealer). You’ll see axle “sales codes” such as DMF (3.21), DMC (3.55), or DMH (3.92), and whether you have Anti-Spin (DSA).
  • Window sticker: If available, it usually lists the optional axle ratio and any towing/off-road packages installed.
• General industry tips
  • Door-jamb RPO stickers are a GM thing; Ram doesn’t use GM-style RPO labels. For Ram, rely on the axle tag and the Mopar build sheet.
  • You can also decode the ratio by rotating the driveshaft and counting tire rotations (with the rear axle safely raised), but use proper safety procedures.

Towing vs MPG impact

• Lower numerical ratio (e.g., 3.21): Best highway fuel economy. At a given road speed, engine RPM is lower, especially in the deep overdrives (0.67–0.64). Great for lightly loaded commuting and long trips.
• Mid ratio (3.55): A solid all-rounder for mixed city/highway and moderate trailers. Works well with the broad 8-speed torque multiplication and the available Anti-Spin.
• Higher numerical ratio (3.92): Best for heavier trailers, frequent grades, or larger tires. It keeps the engine closer to its torque peak and reduces hunting between gears.

Rule of thumb: Jumping from 3.21 to 3.92 raises engine RPM roughly 22% at a given speed. That improves launch and grade performance but will trim highway MPG. The 8-speed’s short 1st gear (4.714, or 5.000 in the TRX) and dual overdrives help offset some of the trade-offs, so pick based on your heaviest regular load, not one-off trips.

Common issues and maintenance tips

While the 2019–2023 DT-generation Ram 1500 driveline is generally robust, owners and technicians have reported the following on some trucks:

• Ring-and-pinion whine: A faint howl at steady speeds (45–70 mph) can point to gear mesh or pinion depth issues. It may be more noticeable with 3.92 sets and under light throttle. Proper setup and quality gear oil are key after any gear swap.
• Carrier/pinion bearing noise: Growling that changes with speed (not engine RPM) can indicate bearing wear. Address early to avoid metal debris circulation.
• Limited-slip clutch chatter: Anti-Spin units can chatter on tight turns if the friction modifier is depleted. Use the correct spec gear oil and additive; a fluid change often restores smooth operation.
• Pinion seal seepage: Watch for oil at the yoke. Fix promptly; low oil accelerates wear and can lead to whine.

Service pointers:

• Use the correct API GL-5 gear oil viscosity per your axle and climate; add Mopar friction modifier for Anti-Spin if the fill doesn’t already include it.
• After towing, off-roading, or water crossings, inspect fluid condition and vent lines.
• Tire size changes effectively alter overall gearing. If you upsize significantly, consider a ratio change (e.g., to 3.92) and recalibration for speedometer/shift scheduling.

Find a driveline shop on Repairius.