Chevy Pickups 101: What’s the Differential?

What an axle ratio means and why picking the right one is important

2012 Chevrolet Silverado 2500HD

 

Technologies like advanced turbodiesel V-8 engines or hydroformed steel frames have advanced the Chevrolet Silverado to unprecedented levels of capability for fullsize pickups. In just the decade since the 2003 model debuted, maximum towing capacity for a Silverado HD has risen 43 percent, from 16,100 pounds to an industry-leading 23,100 pounds.

Getting that towing force from the engine to each rear wheel is the task of a set of gears located in the center of the truck’s rear axle known as the differential. The ratio of the sizes of those gears is represented by the diameter of the gear that drives the wheels in relation to the gear from the driveshaft. So, a 3.08:1 ratio indicates the drive gear has 3.08 times as many teeth as the gear on the driveshaft.

Using different diameter gears within the differential affects both towing ability and fuel efficiency. Since pickup owners have varying needs and preferences, Chevrolet addresses different requirements by offering various rear axle gear ratios.

“A numerically lower axle ratio keeps engine speeds lower for better fuel economy, while higher ratios generally yield higher towing capacities and quicker launches from a stop,” said Robert Crotty of Crotty Chevrolet Buick in Corry, PA.

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