Mechanical lockers

Mechanical Differential Lockers

Mechanical differential lockers, commonly referred to as "lockers", are drivetrain devices designed to improve traction by forcing both wheels on an axle to rotate at the same speed. For overlanders traveling in remote or low-traction environments, lockers provide a highly reliable method of maintaining forward motion when one or more wheels lose grip.

What Is a Mechanical Locker?

Under normal conditions, an open differential allows wheels on the same axle to rotate at different speeds. This is necessary for smooth cornering on high-traction surfaces but becomes a disadvantage off-road, as torque is directed to the wheel with the least resistance.

A mechanical locker overrides this behavior by locking the axle shafts together, ensuring equal torque delivery to both wheels regardless of traction differences.

Types of Mechanical Lockers

Mechanical lockers are available in several forms:

• Selectable lockers – Engaged manually by the driver via a switch, lever, or air system
• Automatic lockers – Engage and disengage based on torque and wheel speed differences
• Spool or welded differential – Permanently locked (generally unsuitable for overland travel)

Selectable lockers are preferred for overlanding due to their flexibility and reduced impact on normal driving.

How Lockers Improve Traction

When one wheel loses traction (e.g., lifted wheel, mud, loose rocks), an open differential sends power to the slipping wheel. A locker prevents this by ensuring:

• Both wheels receive equal torque
• Vehicle can move even with only one wheel having traction
• Momentum is maintained with minimal wheelspin

This is particularly valuable in cross-axle situations, steep climbs, deep ruts, and rocky terrain.

Proper Use of Mechanical Lockers

Lockers should be used deliberately and only when needed:

• Engage before entering an obstacle
• Use at low speeds
• Combine with low range gearing
• Disengage once traction improves

Driving with lockers engaged on high-traction surfaces can cause drivetrain binding, increased tire wear, and steering difficulty.

Importance for Overlanders

For overlanders, mechanical lockers offer several key benefits:

• Increased self-recovery capability
• Reduced reliance on momentum
• Lower risk of getting stranded in remote locations
• Less strain on throttle and clutch due to controlled crawling

In remote travel, the ability to progress slowly and predictably is often more important than outright speed.

Limitations and Considerations

While effective, lockers have trade-offs:

• Reduced steering ability when engaged
• Increased drivetrain stress
• Higher cost and installation complexity
• Potential learning curve for new drivers

Training and experience are essential to use lockers safely and effectively.

Conclusion

Mechanical differential lockers are among the most powerful traction aids available to overlanders. When used correctly, they significantly expand a vehicle’s capability in difficult terrain while enhancing safety and control. Their importance lies not in aggressive driving, but in enabling slow, deliberate progress where traction is limited.