Axle ratio. It’s one of those techy optional items buyers of new pickups ask questions about a lot. Probably more so than tow ratings and engine options.
That’s because manufacturers don’t think informing buyers about axle ratio options helps sell their trucks or plays into a buyer’s ultimate decision-making process.
So there’s very little, if any, axle ratio information in their brochures or on their websites.
But choosing the right axle ratio does make a difference in how a pickup performs, be it empty, towing a trailer or hauling a heavy load in the bed. Axle ratio also affects fuel economy on the open highway.
So here’s the short take on how to choose the best axle ratio:
When it comes to fuel economy, look at the axle ratio as the amount of fuel burned over a given amount of time when the truck is running at highway speeds.
For example, a truck with a 3.31 axle ratio would burn less fuel at highway speeds than one with a 3.55 ratio. That’s because the 3>31 ratio keeps the engine rpm lower than would the 3.55 ratio.
Likewise, a 3.55 ratio would get better mpg at highway speeds than it would equipped with 3.73s – all other things being equal.
How much better mpg? In general, about .5-1.0 mpg at 65 mph per .25 increase in axle ratio.(It’s important to note that in city driving there’s negligible difference in fuel economy between axle ratios.)
The larger the axle ratio number, the quicker the truck will accelerate. For example, a truck equipped with 3.55:1 axle gearing will accelerate faster than one equipped with a 3.31 axle ratio.
Similarly, a pickup with a 3.73 axle ratio will be faster than one with 3.55s. It does’t matter whether the truck is empty or loaded. It’s pure mechanics.
Best towing ratio
In general, the best towing axle ratio for most of the post-2010 pickups is in 3.55 or 3.73. Those ratios provide very good acceleration with gas V-8s and diesels.
Trucks equipped with eight-, nine-, or 10-speed automatics may work well with 3.31 ratios as the new transmissions have lower 1st and 2nd gears than the old four, five and six speeds, helping offset the axle ratio acceleration deficit.
Best MPG ratio
If getting the best fuel economy is priority, then choose the lowest numerical number offered, such as 3.08, 3.23 or 3.31. This applies to highway driving; city driving mpg isn’t really affected by the axle ratio. If you do a mix of both, go with the “standard” axle ratio offered by the manufacturer.