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Do max towing packages with higher rear axle ratios impact MPG?


For decades, conventional wisdom said higher rear axle ratios impact MPG poorly, and you need to be careful with max towing packages. Is that still true?

When shopping for a new truck, there are a lot of things to consider like max towing packages with higher rear axle ratios and the impact on fuel economy. This can be critical if you are an occasional tower or a never tower with how you use your truck.

The thinking is a rear axle ratio improves the way the truck pulls a trailer while sacrificing MPG. Typically the higher number (aka 4.10 rear axle ratio), the better for towing, the worse for MPG. A lower number like a 3.23 is often referred to as highway gears and really meant for fuel economy and not towing.

This topic comes up quite a bit, and here’s a recent example with a question that came from a viewer who is shopping for a new truck.

Do higher rear axle ratios impact MPG?

Kevin J. writes:

Hey Tim,

I am looking to purchase a 2023 Silverado 1500 LTZ with the 3.0l and came across your YouTube channel while researching the truck. I watched your videos on your high country; very informative.

I see your truck has the 3.73 gear ratio, I am wondering if you have any information on what the fuel mileage does compared to the 3.23, 3.42 and the 3.73 along with the performance of the truck.

Any information would be appreciated.

For this question I asked General Motors, searched online and recalled other experiences in my past decade plus of covering trucks.

Here’s what I found.

First, General Motors responded with this statement:

I can tell you there is no difference in the MY23 LZ0 EPA fuel economy label between a non-Tow Package with a 3.23 axle and the Tow Package version that comes with the 3.73 axle. And this is true for both the 2WD and 4WD trucks. Only the 3.23 and 3.73 axles are available with the LZ0.

– Sean Szymkowski
Senior Manager, Chevrolet Trucks Communications

Next, I searched online, and I found most people think it is about a half MPG from various forums and posts I saw.

Also, unfortunately, Fuelly.com, a pretty decent online MPG resource website, doesn’t separate trucks out by rear axle ratios.

From my knowledge I can say this thinking is a bit old school vs. new school trucks. For example, a few years ago I was driving the new versions of the Chevy Silverado HD trucks, and they had switched from the 4.10 rear axle ratio to 3.73 rear axle ratio. When I asked an engineer about this, he mentioned they didn’t need the more stout 4.10 rear axle ratio anymore thanks to the newer transmissions they are using with various drive modes. Basically, they have more gears and they can manipulate those gears to act like the truck has the 4.10 rear axle ratio.

Also, they can lock out gears. When I towed with the Ford F-150 PowerBoost I bought a few years ago, Ford would actually lock out the top two gears when towing. Instead of offering all 10 speeds, the truck only allowed you to have 8 speeds. This, and the software programming with tow/haul mode, allowed them to replicate the benefits of the higher ratio gears without sacrificing any perceived fuel economy differences compared to a smaller gear.

While you still get a higher gear ratio with a max towing package, you don’t have to pay the MPG price for the more stout rear end.

The bottom line

Once all the rage, the stout rear end ratios are slowly going away thanks to mechanical and software improvements. There are still several benefits still to a max towing package — such as additional transmission cooling and a larger rear axle overall — but the rear axle ratio isn’t the end all be all like it used to be, and you don’t suffer a MPG drop by getting it.

Tim Esterdahl

Automotive Journalist Tim Esterdahl has been a lover of trucks and SUVs for years. He has covered the industry since 2011 and has pieces in many national magazines and newspapers. In his spare time, he is often found tinkering on his '62 C10 pickup, playing golf, going hunting and hanging out with his wife and kids in Nebraska.

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