Date Published: January 29, 2026 | Last Modified: 1 hour ago | 4 minute read | Verified by Mitchell Bazinet at Redwater Dodge

Mastering the Rockies: Why the 4:10 Axle Ratio is Non-Negotiable for RAM Heavy Duty Owners

What is the best gear ratio for towing 20,000 lbs in the mountains?

The Science of the "Short" Gear

In the world of RAM Heavy Duty trucks (RAM 2500 and RAM 3500), the gear ratio refers to how many times the driveshaft rotates for every single rotation of the wheel. A 4:10 ratio means the driveshaft turns 4.10 times for every wheel revolution.

In technical terms, this is a "lower" gear ratio compared to a 3.73. By allowing the engine to operate at a slightly higher RPM at a given road speed, the 4:10 ratio places the engine deeper into its power band. This delivers:

Massive Torque Multiplication: More mechanical advantage to get heavy loads moving from a dead stop.

Reduced Drivetrain Stress: Because the engine and transmission don’t have to work as hard to overcome inertia, you reduce heat buildup and long-term wear on your Cummins® Turbo Diesel or HEMI® V8. 

Enhanced Engine Braking: Essential for those long descents back down the mountain.

Why Alberta Demands More from Your RAM

Towing in high elevations presents a unique challenge: air density. Even with modern turbocharging, your powertrain is under immense pressure when climbing through the Rockies. A 4:10 axle ratio provides the mechanical "grunt" needed to maintain stable speeds without constant gear hunting.

As Mitch from Redwater Dodge notes, "A lower gear ratio delivers more torque to the wheels, giving you stronger pulling power and better control on steep grades." In Alberta, "control" isn't just a luxury, it’s a safety requirement.

The Fuel Economy Conversation

The most common question we get is: "Will a 4:10 gear ratio ruin my fuel economy?" The honest answer? When your truck is unloaded and cruising on flat highways, you may see a slight dip in MPG because the engine is turning at higher RPMs. However, RAM’s advanced 8-speed and Aisin 6-speed transmissions are designed to mitigate this, offering overdrive gears that keep cruising speeds efficient.

Crucially, when you are loaded, the 4:10 ratio often proves more efficient than a higher gear. Why? Because the engine isn't struggling, downshifting, or lugging to maintain speed. It stays in the "sweet spot," ultimately saving you fuel and frustration during the haul.

Factory-Built vs. Aftermarket: Getting it Right the First Time

While it is technically possible to re-gear a truck after purchase, it is a costly and complex process that can sometimes lead to warranty complications or vibrations if not shimmed perfectly.

Choosing a RAM Heavy Duty with a factory-installed 4:10 ratio ensures that your truck is calibrated from the assembly line for that specific torque output. It saves you time, money, and guarantees that every component—from the speedometer to the traction control, is perfectly synced.

Additional Gear Ratio Questions & Answers

Q1. Can I tow 20,000 lbs with a RAM 2500, or do I need a 3500?

A1. While certain RAM 2500 configurations are highly capable, towing 20,000 lbs typically puts you into RAM 3500 territory, especially when considering payload and pin weight for a fifth-wheel or gooseneck hitch. Always check your specific door jamb sticker for the Max GVWR.

Q2. How does the 4:10 ratio affect my 0-60 mph speed?

A2. Generally, a 4:10 ratio improves off-the-line acceleration (your "hole shot") because it gets the engine into its power band faster. It makes the truck feel much "zippier" in city driving, though it reduces the theoretical top speed.

Q3. Is the 4:10 ratio available on both Gas and Diesel RAMs?

A3. Yes. Whether you choose the 6.4L HEMI® V8 or the 6.7L Cummins® Turbo Diesel, the 4:10 axle ratio is an available option designed to maximize the towing potential of both powerplants.

Q4. Does the 4:10 ratio require special maintenance?
A4. The maintenance schedule remains largely the same, but because these trucks are often used for "Severe Duty" towing, we recommend more frequent differential fluid inspections to ensure the gears remain cool and lubricated under heavy loads.