What Is A Lunchbox Locker And How Does It Work?

There are different kinds of lockers out there, and each once of them works differently. Each type of locker has its own pros and cons. In our experience, lunchbox lockers are the most popular, especially when you’re on a budget. The name lunchbox comes from the idea that you pack different lunches in the same reusable box. In this case, the stock carrier is the box, and the locker is the lunch.

How Does It Work?

The lunchbox locker is designed to split power evenly between both wheels regardless of which wheel has traction. But, it has to remain open in normal driving situations to allow for the differential to work properly. This is a massive improvement over the standard open differential which can send all of its power to the wheel with the least traction.

lunchboxlocker

Lunchbox locker diagram without the center pin.

In a lunchbox locker, the hole where the center pin goes through is shaped like an oval instead of a perfect circle. When torque is applied, it forces the pin to move a little bit. When the pin moves it pushes the cam gears into the axle gears, locking them together.

When torque isn’t applied the pin returns to the center of the oval and stops pushing the cam gears outwards. This allows the cam gears to spin right past the axle gear which is what creates the ratcheting noise that lunchbox lockers are famous for.

How It’s Installed

The lunchbox locker replaces the factory spider gears inside of the stock carrier. This means that when you install a lunchbox locker you don’t need to reset your backlash. You can actually install one of these lockers without even removing the differential from the axle housing. This is much easier than most lockers which require fully disassembling the different since most lockers replace the entire carrier.

Locker that replaces the entire carrier.

A locker that replaces the entire carrier.

Pros and Cons

The extremely simple design of the lunch-box does create a couple of issues. Lunchbox lockers make a very loud ratcheting sound when they’re cornering. They also have a tendency to unexpectedly lock and unlock. They’ll randomly lock and unlock because of how we corner in vehicles.

If you stay at exactly the same speed or decelerate in a corner the locker is fine and behaves how you would expect. However, if you have to accelerate for any reason the locker can pop into its locked position very violently. This can create unsafe handling characteristics. Due to the fairly violent locking and unlocking mechanic, lunchbox lockers are notoriously short lived.

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Notice the oval shape where the pin resides.

Although the simple design does create some problems, it makes these types lockers very cheap. Many lunch-box style lockers cost only $200-$400, while more advanced lockers can cost as much as $2,000. They are also super easy to install and require pretty much no maintenance.

Summary

Lunchbox lockers have an extremely simple design that helps keep the cost low but can introduce issues with on road handling. They’re super easy to install and are great if you want to have a locker in your rig for cheap.

If you plan on buying a lunchbox locker we recommend buying one for your front axle. This will almost entirely get rid of the on-road handling issues since your rig will be in 2WD on the road and the locker won’t lock/unlock randomly. Let me know if this short article was helpful in the comments below!

About the author

Bryce Cleveland

Bryce has been in the automotive industry for most of his life. He’s done everything from fixing cars, flipping cars, writing about cars, and everything in-between. He has owned a total of 18 vehicles, most of which he owned before the age of 20. He currently drives his 2015 Ford Fiesta ST every single day and has plans to buy his third Jeep XJ Cherokee very soon.
Read My Articles

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