What Is a Locking Differential?

What Is a Locking Differential?

Last Updated January 3, 2022 | Alison Smith

Before we can comprehend the role of a locking differential, we should have a basic understanding of how a standard open differential operates. Most vehicles are going to be equipped with an open differential, which sends power from the engine to the axle, allowing the wheels to spin at different speeds while turning a corner. As the distance each wheel has to travel varies, the outer wheel will be traveling faster than the inner wheel that has a shorter length to travel.

Typically, the wheel experiencing the least amount of traction will receive the most power. As they are suitable for most on-road driving conditions, most two-wheel-drive vehicles feature an open differential. They are also more affordable than a locking differential, which can be found in many four-wheel-drive vehicles.

What Is a Locking Differential?

Locking differentials allow both wheels to travel at the same speed, so when traction is lost for one wheel, both wheels will still keep spinning regardless of the amount of resistance. They can be added to either the front or rear axle, or even both axles if you’re planning on doing some hardcore off-roading. For example, if you’re crawling up a rocky trail and one of your wheels ends up dangling free in the air, an open differential is going to send all the power to the wheel experiencing the least resistance.

2018 Toyota Tacoma Locking Differential

So while that wheel is spinning freely, the wheel still maintaining contact with the ground will be stationary. That’s not really going to help the situation at all. With a locking differential, since equal power is transferred to both wheels, the one wheel with ground contact will be able to rotate along with the free wheel, propelling the vehicle forward to freedom. Because of the added traction, locking differentials are great for off-roading, which is why they are frequently found in Jeep Wranglers, trucks, and other 4x4 rigs.

Brake lock differentials serve a similar purpose as diff locks but are not the same thing and cannot be substituted for a full-on locking differential. There are two main types of locking differentials: automatic and selectable.

Automatic Lockers

Automatic locking differentials are exactly what they sound like: Diffs that lock automatically without requiring the driver to do anything. Some automatic locking differentials, or full-time lockers, only unlock depending on the driving conditions, meaning that all other times the diffs are locked.

A prime example of this is the Detroit locker, which only has three ratchet gears and remains in a locked position unless otherwise acted upon by an outside force, requiring the wheels to spin at different speeds. So because it is constantly in a locked position, the Detroit locker is great for off-roading and trailblazing, but it’s not going to be optimal for street riding or daily highway driving. Be careful if you have a vehicle with a short wheelbase, such as a two-door Jeep Wrangler, because automatic lockers that remain in a closed position can be a bit dangerous or squirrelly when it comes to road handling.

2018 JL Wrangler Electronic Locking Differential & Heavy-Duty Axles

Other auto-locking diffs are the opposite, which means they only lock automatically when necessary. Lunchbox lockers, also known as drop-in lockers, for example, are a simple way to convert an open differential into one that locks. These lockers drop inside a factory differential carrier and replace the original stock spider gears. They are called lunchbox lockers since they are basically just a new component in the old diff housing. When torque is applied, the lunchbox lockers will activate and allow even power dissipation. These are a relatively affordable option as they don’t replace the entire differential. Having lockers that only lock when absolutely needed is going to make the system last longer and prevent unnecessary tire wear.

Since automatic lockers don’t let you have full control over your differential, they can be a bit awkward when driving on the road and put more stress on the vehicle as well as the tires. They can also be loud when they lock and unlock, which can be quite annoying after a while. Unlocking and locking can also happen at random inconvenient times while driving. If you’re looking to have a strictly off-road vehicle in your garage, then an automatic locker might be a less expensive, more practical option than the next type of locking differential.

2018 JL Wrangler Diff Lock Switch

Selectable Lockers

While the driver has little to no control over automatic locking diffs, selectable lockers grant the freedom to switch between a locked and open differential freely. While electric lockers are more common in modern vehicles, cable or air lockers will accomplish similar results. Although selectable lockers, also known as manual lockers, are typically more expensive than automatic lockers, they will be more durable and cause fewer problems in the long run. Air lockers utilize a compressor system that can lock the differential with the push of a button. Upon activation, the pneumatic locking system stops the gears from rotating, thus locking the diff. Unless the air locker is activated, then the differential will remain in the open position, which is perfect for those who have rigs that double as a daily driver and an off-roading beast. However, if not installed properly, they can leak and cause a variety of issues.

Electronic lockers, sometimes referred to as e-lockers, are similar to air systems as they only require the push of a button to initiate the diff lock. In a basic sense, e-lockers send an electrical current that activates the locking system, closing the previously open differential. The Jeep Wrangler’s off-roading model, the Rubicon, features Tru-Lok front and rear electronic locking differentials that can be initiated with the flip of a switch. Once the lockers are engaged, power is distributed evenly between the wheels for enhanced off-road performance and rock crawling capabilities. Having a selectable locker really makes your vehicle versatile enough to handle all your daily driving needs during the week as well as your off-roading excursions when Saturday rolls around.

A cable-operated locker uses a cable-shifting system that is connected to the locking mechanism. Typically equipped with a manual shifter, some can be converted to an electric switch. While similar to air lockers, cables can be a bit more sturdy and durable. However, they can still be damaged if installed improperly or used incorrectly. So while selectable lockers are going to have a lot more moving parts than an automatic locker, they offer greater control and drivability. Due to the automatic locker being simpler, it would be easier to fix if something goes awry.

Locking Differential Pros

Selectable lockers may provide more benefits than automatic diff locks, but either one is going to improve off-roading performance and capabilities when it comes to tackling tough obstacles on the trail. Here are a few reasons why you may consider investing in a locking differential.

  • Distributes power evenly to the wheels
  • Enhanced off-road performance
  • Improves traction in rough terrain
  • Can be equipped for the front axle, rear axle, or both
  • Some can be activated with the push of a button
  • Selectable lockers are great for daily drivers

2018 JK Wrangler Tru-Lok Differentials

Locking Differential Cons

While locking differentials will be beneficial to most people who plan on doing some wheeling, there are a few negatives to ponder. Selectable lockers, despite their higher cost, will offer more positives than automatic lockers. However, they are a bit more complex, which means that if a problem occurs, it will be a less straightforward fix than a simpler automatic locker. Here are some cons of a locking differential:

  • Higher cost for selectable lockers
  • Tire chirping or barking when cornering
  • Clunky engage and disengage for automatic lockers
  • Can put added stress on driveline components if misused
  • Selectable lockers can be complicated to fix if they break down

Depending on how you use your vehicle, perhaps the standard open differential is all you need. But if you want a taste of the great outdoors and plan on doing quite a bit of off-roading, then you really can’t go wrong with a locking differential!

Alison Author Photo

About the Author

Alison is the author of over 100 articles on CJ’s resource center. She’s used her inquisitive nature to help millions of readers learn more about their favorite vehicles. Read full bio →

Sources: Differential Locker Comparison, Crawlpedia | What's The Diff? We Look at Lockers and Limited Slips with Eaton, Off Road Xtreme | Improve Off Road Performance With a Locking Differential, MotorTrend | Image Credit: jeep.com, toyota.com

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What Is a Locking Differential?

A differential is a critical component of every vehicle, but what exactly is a locking differential? While similar to a standard, or open, differential, a diff lock allows equal amounts of torque to reach both wheels at the same time rather than spin at different speeds. Locking differentials are great for off-roading, especially in tricky situations where you may need a little extra traction.

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