For those unfamiliar with traction devices in off-road vehicles, lockers can be a true game changer. They greatly enhance capability and unlock new possibilities for four-wheel-drive performance. Once a vehicle is equipped with one of these systems, the difference is significant—especially for those who have previously dealt with the limitations of open differentials.
Open Differentials (What They Are and Why They Suck)
Most Jeeps from the factory come with an open differential, which is a simple mechanical design. Axles enter from each side and engage spider gears. These gears, in turn, engage a center gear held in place by a pin within the carrier assembly. The ring gear is attached to the carrier, which is rotated by the pinion gear, thus turning the axles.
The primary issue with open differentials is their torque distribution. All of the engine’s torque is directed toward the wheel with the least amount of traction. For example, if one wheel is suspended in the air and the other is on solid ground, the wheel with no traction receives all the power—leaving the vehicle immobile. This design, while beneficial for on-road driving manners, severely limits off-road capability. In practice, a vehicle with open differentials effectively operates as a two-wheel drive, delivering power to only one wheel at each axle.
Diagnosing an Open Differential
It’s possible to identify whether a vehicle has an open differential without removing the cover. By jacking up the rear axle so both wheels are off the ground and rotating one wheel, the other should spin in the opposite direction—indicating an open differential. If both wheels rotate in the same direction, the axle is likely equipped with a traction device.
Traction Devices Categories and Differences
Lockers can be broken down into two main types:
1. Automatic Lockers
These do not rely on clutches and instead physically lock both axles together so they rotate at the same speed. Automatic lockers include “lunchbox lockers” (such as those by Aussie, Lockright, and Yukon), which are cost-effective because they replace only the spider gears. Gear setup is typically not required, and in many cases, installation can be done without removing the carrier from the axle.
Drawbacks:
Automatic lockers are known for being noisy and can create unusual handling characteristics on the road. They may cause unintended lane changes as they engage or disengage unpredictably. This behavior can be particularly hazardous in icy or snowy conditions.
Other automatic lockers, such as the Detroit Locker, are full-carrier replacements that require a full gear reset but offer greater strength and reliability than lunchbox styles. These are preferred when maximum durability is required.
2. Selectable Lockers
Selectable lockers allow the driver to manually engage or disengage the locking mechanism via electric, air, or cable actuation. When disengaged, the differential operates like an open differential, maintaining smooth road manners. When engaged, both axles are locked together, significantly improving off-road traction.
Types of Selectable Lockers:
Selectable lockers allow the driver to manually engage or disengage the locking mechanism via electric, air, or cable actuation. When disengaged, the differential operates like an open differential, maintaining smooth road manners. When engaged, both axles are locked together, significantly improving off-road traction.
Electric lockers (e.g., Eaton E-locker):
Many Jeep Rubicon models come equipped with factory-installed electric lockers, which are electronically actuated via a small servo motor located within the differential housing.
Air lockers (e.g., ARB):
These utilize an onboard air compressor to engage the locking mechanism. The ARB is among the most well-known products in this category.
Cable-actuated lockers:
Cable lockers offer a mechanically simple and highly durable solution. The system eliminates the need for electronics or air lines, making it exceptionally reliable in harsh conditions.
Advantages of Selectable Lockers:
- Excellent road manners when disengaged
- Minimal tire wear
- Strong and reliable—especially in front axle applications
- Full locking capability when engaged
Disadvantages:
Generally expensive
Require full gear setup
Installation complexity varies depending on the system:
Air lockers require mounting and wiring a compressor
Cable systems involve precise mechanical routing
Electric lockers require wiring and electrical integration
A common recommendation is to install a selectable locker during a gear change, minimizing the cost of labor by combining both procedures.
3. Limited Slip Differentials (LSDs)
Limited Slip Differentials offer a middle ground between open differentials and full lockers. Instead of locking the axles together, they use clutch packs or gear-based torque transfer systems to direct torque to the wheel with more traction.
Most LSDs feature a modified carrier design to accommodate internal components such as clutch discs and springs, which apply friction to the spider gears. When one wheel loses traction, friction from the clutch packs transfers some torque to the other wheel, improving forward motion and reducing the chance of getting stuck.
LSDs generally struggle in more technical off-road conditions—such as rock crawling—especially when paired with oversized tires. The clutch mechanisms are not strong enough to fully lock the axles under high-stress situations.
4. Spools Differential
Spools are the most extreme form of axle locking. They permanently lock both axles together as if they are a single solid shaft, with no allowance for slippage or differentiation.
Due to their aggressive locking nature, spools are recommended only for dedicated off-road or competition vehicles, where road compliance is not a concern.
Conclusion
- For a mix of daily driving and off-road, gear-based LSDs like the Eaton TrueTrac offer excellent performance with minimal drawbacks.
- For serious off-roaders with a flexible budget, selectable lockers provide unmatched versatility.
- For competition builds or trail-only rigs, spools are strong and affordable—but not suitable for road use.
Whether you’re building a rock-crawling rig, upgrading your off-road truck, or looking to optimize your work vehicle for unpredictable terrain, a differential locker can make all the difference. Want to find the right locker solution for your vehicle? Contact our team today or explore our full range of locking differentials designed for serious performance and durability.
