Axle spec’ing on 2019 Ford, GM & Ram 1/2-ton trucks

Quimby Mug Bayou Florida
Updated Aug 20, 2018
2019 Ram 1500 – Max Tow Axle

About 30 years ago, my dad had my brother, a mechanic, put a new set of gears in the rear differential of his truck. Dad had been having trouble towing his boat up a steep boat launch and thought a lower gear ratio would do the trick. He was right.

That lesson has always stayed with me—that and the subsequent drop in gas mileage. Dad’s truck ended up getting around 12MPG after that. But he knew what he was getting into and was more concerned about yanking his boat out of the water than maximizing fuel economy.

Such is the case when it comes to spec’ing axle ratios in pickups: truck use dictates ratio selection while fuel economy usually takes a back seat. Of course things have changed a lot from 30 years ago. Fuel conscious eight and ten-speed transmissions offer a lot more advantages than their older counterparts.

To help you get a better sense of available axle ratios for ½-ton trucks, we reached out to major OEMs to fill us in on their latest numbers.

As a reminder, a lower (numerically higher) gear ratio, such as 3.55:1 to 4.10:1, provides more low-speed wheel torque, which means it takes more throttle to get the vehicle and the load it’s carrying or towing moving. In the case of a gear ratio like 3.55:1, the driveshaft will have to turn 3.55 times to complete one wheel revolution, hence the ratio 3.55 to 1.

Lower gear ratios are ideal for getting heavy loads moving or taking on steep terrain, but the more the driveline has to turn, the more fuel the engine has to consume. Again, it all comes down to the capability that you’re after.

If you’re not sure of your current truck’s axle ratio, you’ve got some options: open the driver’s side door and look for the axle ratio code on the truck’s vehicle identification plate; lift the truck, mark the driveshaft and rear tire with chalk and turn the driveshaft by hand until the wheel makes one complete turn (truck has to be in neutral; accuracy can be improved with a makeshift pointer mounted near the driveshaft); crack open the diff and look for the stamped gear numbers (the most revealing, but toughest approach).

When applicable, we posed the same axle ratio questions to each OEM and have printed their responses below. Scroll down a little farther and you’ll find helpful axle ratio charts for 2019 year model ½-ton trucks from Ford, GM and Ram. Nissan and Toyota did not respond to interview requests.

Ford

HWT: Has Ford’s 10-speed transmission affected axle spec’ing in any way? If so, how?

Ford: We have not seen any major shifts in our customer axle selection since the implementation of the 10-speed transmission across our powertrain lineup. Revised low-end and reverse gearing allowed us to utilize the same axle ratios on which the market has come to depend.

HWT: Did Ford’s 10-speed transmission bring about any new axle specs? Did it make any obsolete? If so, which ones?

Ford: See response above

HWT: Where does axle spec’ing rank among fleets? Is it one of the more important specs? Please explain.

Ford: Correct axle spec’ing is extremely important for fleets. Improper rear end ratios, axle capacities, and axle capabilities can severely impact a truck’s ability to get the job done.

A truck without a high enough rear axle ratio might perform well at highway speeds, but might be slow to start while hauling a heavy load. Gradeability and startability are both distinctly impacted by axle ratio.

A truck spec’d without a locking rear-axle could have difficulty in some off-road situations when equal force is required at each rear wheel. Consider pulling a trailer up a grade on wet concrete. A locking rear end would allow each of the rear wheels to turn at the same speed. Without it, the force might be transferred to the wheel with the least resistance causing wheel spin. Correct attention to the duty cycle of the vehicle is vital to spec’ing the best truck for the application.

In all, there are a number of considerations that must be factored in when spec’ing a rear axle. Gradeability, Startability, average speed, load requirements, terrain, and even tire size to name a few all impact rear-axle requirements.

HWT: What’s a popular axle spec for an F-150 two-wheel drive fleet truck? F-250 two-wheel drive?

Ford: F-150 and Super Duty both have a strong balance of rear axle ratios in 4×2 trucks. The most important thing is which rear axle ratio best fits the needs of the individual fleet, and the duty cycle of the fleet vehicle under review. A fleet with 10 trucks might have 10 distinctly different duty cycles, from continuously pulling load at grade to driving unladen on flat ground all day. Heavy loads typically need a bigger gear, while an unladen truck on flats might be better suited for a lower ratio. Proper spec’ing will give you more functional trucks.

HWT: What are the available axle specs for F-150 and F-250 two wheel drive fleet trucks?

Ford: F-150 axle ratios range from 3.15:1 Non-Limited-Slip up to a 3.73:1 Electronic Locking. F-250 Super Duty offers a wide variety of rear ends, from a 3.31:1 Non-Limited-Slip to a 4.30:1 Electronic-Locking axle.

GM

HWT: Has GM’s 10-speed transmission affected axle spec’ing in any way? If so, how?

GM: What’s worked well for our customers is to optimize axle ratios for each powertrain combination based on performance and fuel economy. For example, the all-new Chevrolet Silverado 1500 trucks have two axle ratios, which are determined by the engine/transmission combination.  The only, “selectable” axle ratio is included with the Max Trailering Package (NHT). 

HWT: Did GM’s 10-speed transmission bring about any new axle specs? Did it make any obsolete? If so, which ones?

GM: Alternatively, our 2018 or “current-gen” Silverado 2500HD gas-powered models offer a choice of 3.73 and 4.10 axle ratios for fleet customers. 

Why are we offering less options? We wanted to simplify the truck-buying process for our customers. Our talented team of engineers understand how to fully optimize our trucks by considering engine capabilities, transmission gear ratios, tire sizes, and more.

HWT: Where does axle spec’ing rank among fleets? Is it one of the more important specs? Please explain.

GM: No response

HWT: What’s a popular axle spec for a GM (GMC and Chevy) 1500 two-wheel drive fleet truck? 2500 two-wheel drive?

GM: No response

HWT: What are the available axle specs for 1500 and 2500 two-wheel drive fleet trucks?

GM: See order guide details for the engine/axle ratio/GVWR charts for our all-new 2019 LD Crew & Double Cabs. (See chart below). 

Ram

HWT: Has Ram’s latest transmissions affected axle spec’ing in any way? If so, how?

Ram: We are using the same 8-speed transmission with upgraded components. Although we did add the new eTorque mild hybrid system to the V6 standard and V8 optional, the optional gear sets are the same.

HWT: Where does axle spec’ing rank among fleet customers? Is it one of the more important options? Please explain.

Ram: Ram Commercial customers can spec a truck for its purpose. If the truck spends most of its days running delivery routes with a medium payload then a lower numerical gear ratio is preferred. It will keep the engine RPM lower and reduce fuel consumption. Adding eTorque further improves efficiency. For trucks that tow heavy loads every day, a higher numerical gear ratio increases the trucks capability by giving the engine additional leverage to the tires. Identifying the truck’s use is very important and keeping that truck in its dedicated service will improve efficiency and lower costs.

HWT: What’s a popular axle spec for a Ram 1500 two-wheel drive fleet truck? 2500 two-wheel drive?

Ram: No other automobile offers more options on a single platform than pickups. The Ram 1500 has three different engine options, three cab sizes, 4×4 or 4×2 and up to three different gear ratios. Customers also can opted for a limited slip differential, locker or open. For the Ram 1500 the most popular ratio is a 3:21. For the Ram 2500, it’s a 3:73. 

HWT: What are the available axle specs for 1500 and 2500 two-wheel drive fleet trucks?

Ram: For the Ram 1500, 3:21 and 3:55 (V6 eTorque and V6 EcoDiesel), 3:21 and 3:92 (V8, V8 eTorque and V6 Ecodiesel). (2019 Ram 1500 Max Tow Axle pictured above.)

For the Ram 2500, 3:42 (manual 6 speed); 3:73, 4:10 (5.7 V8 or 6.4 V8); 3:42 (Cummins diesel).

2019 Ford F-150 towing capabilities (includes axle ratios)

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Gm Engineaxle Chart 2 Gm Engineaxle Chart

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