• Deep Dive: General Motors’ G80 Locking Rear Differential

General Motors has been offering an automatic locking rear differential in its Chevy and GMC trucks for more than 40 years. Today, its prevalence has grown to include every body-on-frame, rear-drive vehicle in GM’s lineup – from the Colorado WT up through the leather-lined Cadillac Escalade. And thanks to its order code, most folks know the mechanical locker as the Eaton G80. Here’s how it works.

The G80 is a specialized differential designed by Eaton to work as a low-speed traction aid, offering full lockup during its operation. When in normal conditions, the unit acts as an open differential, letting the rear tires spin independently of each other, with the outside wheel spinning faster during turns. However, when one tire spins 120 rpm faster than the other, the G80 locker kicks into action.

As the video above shows, the difference in rpm actuates a flyweight-type governor, slinging a pawl that engages a clutch system, which then causes a cam plate to ramp against a side gear, compressing the disc pack. This action locks together both axle shafts, and therefore makes both wheels rotate at the same speed. Eaton has included two such actuating pawls, allowing the G80 to work in both forward and reverse gears.

Simply put, the G80 engages automatically and without driver input to evenly distribute power both rear wheels. This is in contrast to other systems as Ford’s or Ram’s E-Lockers, which require the driver to engage the system electronically from the cabin. While there’s pros and cons to both systems, the Eaton G80 does take the cake for simplicity for the driver.

Continue reading to learn more about the Eaton G80 Locker.

General Motors offers the Eaton G80 automatic locking rear differential on all its body-on-frame SUVs and trucks – either as standard equipment or as an optional extra. What’s more, 4WD is not necessary to order the G80.

Currently, the G80 is offered on the Colorado and Canyon; Silverado and Sierra; Tahoe and Yukon; Suburban and Yukon XL; and the Escalade. Both the Z71 and All-Terrain packages, along with many of the upper trim lines, come included with the G80, while other trims offer it as an option.

Why it matters

Speaking from personal experience, the G80 works well at providing the extra traction needed to get through sticky situations. There’s been plenty of times the G80 in my personal vehicle has saved me from calling for a tow. The only real downside is the Eaton’s somewhat clunky operation at high-rpm engagement. There are also reports floating around that suggest oversized tires mixed with an over-zealous right foot will lead to exploding pumpkins. But for the majority of consumers, the G80 works as a decent alternative to aftermarket lockers, limited-slip differentials, or perhaps even 4WD. After all, there must be a reason GM has stuck with Eaton’s design for 40 some years.

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Mark McNabb was a contributor at TopSpeed from 2013 to 2018. Growing up, Mark always had a mind for tinkering on random items throughout his home and dad’s garage, including a 1953 Ford Mainline and 1971 Corvette Stingray.  Read full bio
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Press Release

Trucks need traction to get the job done. And whether it is winter snow, spring mud or the weed-covered boat ramps of summer, an automatic locking rear axle can help keep Chevy trucks moving ahead with enhanced confidence and control.

Often referred to as the G80 for its order code, the rear axle locks automatically if one wheel starts to spin, enabling both rear wheels to propel the truck. The added traction lets a 2WD pickup to go places traditionally thought of as 4x4 territory, and further enhances the capability of 4x4 pickups.

“The G80 locking axle provides a greater traction advantage than limited-slip differentials in most situations, while its automatic engagement requires no driver involvement, unlike some competitors’ electronic lockers, which require driver activation,” said Jeff Luke, executive chief engineer. “The G80’s simplicity, durability and sure-footed grip have been proven with generations of customers, as it has been a staple of the Chevy truck lineup for more than 40 years.”

The G80 automatic locking rear axle is available on most Silverado models, and is standard on LTZ and Z71 versions of the Silverado 1500 and all Silverado 2500 and 3500 HDs. Additionally, it is available on Colorado WT and LT models, and standard on Colorado Z71. It is also standard on Tahoe and Suburban.

With technology by Eaton, the G80 performs as an open differential until excessive slip in one wheel automatically triggers the locking mechanism, ensuring the rear wheels turn at the same speed. It provides more sure-footed traction than a conventional limited-slip axle, which can allow the wheels to turn at different rates in a low-traction environment, limiting the amount of traction-enhancing torque that can be channeled to the faster-spinning wheel. Unlike electronic lockers, the G80 engages and disengages automatically, with no input from the driver.

When the G80 detects excessive wheel slip, a flyweight-type governor engages. A self-energized clutch system causes a cam plate to ramp against a side gear, compressing disc pack to cause both rear axle shafts/wheels to rotate at the same speed.

The lockup and disengagement processes happen instantly and are practically imperceptible to the driver. Ride is smoother because the G80 operates mostly as an open-type differential in normal driving conditions.

“There are no buttons to push or electronic settings to engage,” said Luke. “The G80 does its job instantly and quietly, so drivers can go about their job with confidence.”

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