What Is Locking Differential?

Most two-wheel vehicles have an open differential which allows the wheels to spin independently. The distance each has to travel will vary. They are more affordable than a locking differential, which is usually found on 4WD vehicles. We will review the question of what is locking differential and the differences between the two types.

What Is Locking Differential?

A locking differential allows both wheels to move at the same speed. When one wheel loses traction, both wheels will continue to spin. This feature can be on either the front or the rear axle. To an off-road performance product, the differential locker is an important component. It replaces or sits inside of the differential carrier. A locker will lock both of the axles together so they rotate at the same speed. The power is split between both wheels evenly.

Automatic (Full-Time) Lockers

What is locking differential? Some are automatic, and these activate when the throttle is engaged. The most popular type is the Detroit Locker which allows your wheels to change speed while making a turn. The shafts are locked together as soon as power is applied. They are the strongest and the most preferred style available in vehicles used for rough terrain.

4x4 on desert

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Selectable (Manual) Lockers

Another answer to the question of what is locking differential is selectable lockers, which give you the best of both styles of differential. When the locker is open, it will act like an open differential. Some will behave like a limited slip. When engaged, it will lock completely with no differentiation between the shafts. A selectable locker needs to be activated. When using the Yukon Zip Locker or the ARB Air Locker a small compressor and an airline will be needed. Some of these lockers are electric, while others use cables. This style of locker:

  • Increases maneuverability on or off-road
  • Has excellent on-road traits
  • Is strong
  • Is good for daily driving

Drop-In (LunchBox) Lockers

What is locking differential? Sometimes it takes the form of the drop-in or lunchbox locker, an automatic locker that replaces spider gears found in open differential carriers. You don’t need a carrier or gear ratio change for installation as long as the vehicle does not have a limited slip and has an open carrier. They are usually inexpensive and easy to install. A common one is the Lock-Right.


When asking “what is locking differential”, some will refer directly to the gov-loc, which can be found on GM pickups and are unconventional limited-slip/locker combos. They are known as gov-loc due to how they operate. When accelerating, a governor moves out and up on a slanted side gear. When the RPM’s increase, the governor pressures the thrust block. A small cam gear then forces the limited -slip clutches into place.

vehicle on heavy terrain

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Limited Slips Are Not Lockers

A limited slip cannot replace a locker despite advancements in the design over recent years. Limited slips, such as the Auburn Gear Positraction and the Eaton TrueTrac, use clutch or gear engagement to keep the wheels moving at the same speed. Some may seem to work like a locker, but as you enter extreme terrain, you will find that your vehicle will behave like an open differential. This is because limited slips are not designedto completely lock up.

Welded Spider Gears (Lincoln/Hobart Lockers)

Referred to as Lincoln Lockers, this welded spider gear acts as a spool. Open differential gears are welded together to make the axle shafts turn at the same speed. This is fine if your vehicle is only for off-roadI. It can be created in less than an hour with a welder, a can of brake cleaner, and a drain pan. It’s a cheap solution and effective.


Spools have been used in drag racing and are a staple in off-roading, specifically in mud racing. These lockers are lightweight and very aggressive when used on the street. There is no difference between the shafts. They can be made from a variety of materials and are complete replacement lockers. Randy’s Rig & Pinion is a drop-in style mini spool style. They can take the place of open differential spider gears and are:

  • Cheap
  • Simple
  • Lightweight
  • Strong


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Brake Bias Traction Control

Modern 4×4 vehicles are equipped with brake-bias traction control. This works by manipulating the antilock brake system to individually lock each wheel when it senses one tire is rotating faster than others. By applying brake pressure to the free spinning wheel the differential will engage the other wheels and will find traction to move you ahead.

Locking versus Open Differential

An open differential will work fine until one tire is in the air, the mud, or on a loose surface such as gravel. This can cause you to lose traction and control of your vehicle. With a solid locker, each tire continues to move you forward.


When navigating off-road in a 2WD vehicle you may find one wheel loses traction when power is transferred to the tire with the least traction, or the one in the air. Before there were lockers there was a way to could get enough resistance to get out of this situation.

Maintain throttle speed and press/hold the brake release button. Pull and release the parking brake pumping it rapidly. This causes the vehicle to bounce on the spinning tire seeking traction.

2WD with Rear Lockers

With the advent of the locking differential a new era of traction began. Instead of using the parking brake maneuver, all one need do is engage the rear locker. This feature can be used at any time in a Jeep with an ARB selectable locker. Press the ARB Compressor and the Rear Lair Locker switches. The open differential will close, the wheels lock, and the power is distributed equally to both wheels providing forward motion.


A 4WD vehicle with an open differential provides power to the front and rear axles. With an open differential, power is going to all wheels; but with 4WD you could effectively drive off-road.

side view of open car

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4WD with Lockers

To have true 4WD, both axles are locked. All tires turn at the same speed. Avoid a heavy foot and bouncing. Disengage the lockers when you aren’t using them as your vehicle will be easier to handle when they are open. To put your vehicle into this mode, shift your transfer case to 4 low. Press the Axel Lock button to engage the rear locker. Press it again to engage the front locker.

When both are engaged, toggle between them with a press of the Axle Lock button. When the transmission is in neutral, the locker will need about 15 seconds to fully engage.

Open Differential

An open differential has a set of spider gears allowing the axle shaft to rotate at different speeds. Off-road, this can be compensated for with good driving skills, but they are not as efficient as a 4×4. They are:

  • Cheap, most vehicles come equipped with them
  • Great for on-road driving

4x4 car on huge desert

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We have reviewed different types of differentials on the market and their applications. You can see there are instances where an open differential would be better than a locking one. We hope we have answered the question of “what is locking differential” so that you can make a decision about what would be best for your driving needs.

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