Rubicon's are the only Jeeps to come from the factory with lockers and Dana 44 axles - front and rear. That alone is what makes the Jeep Rubicon the ultimate factory off road vehicle. So what is a locker? In short, a locker 'locks' the left and right wheels together so they both spin at the same speed regardless of conditions. A conventional axle, known as an open rear, sends all the power of the engine to the wheel with the least amount of traction; that will you get you ... stuck. Lockers are not for use in the snow or even wet weather, unless you get stuck. Letting both wheels spin allows the vehicle to slide sideways. When a front locker is engaged it can make turning difficult and it widens the turning radius. There are many types of axles/lockers out there and they all serve a different purpose and they all have their ups and downs.
Basic Differentials: These are the most common style differentials found in stock vehicles. None of these are lockers but rather what is removed/changed to install a locker.
Open Rear: This is the most basic rear available, fine for daily driving and fuel economy. It transfers all power to wheel with the least resistance - perfect for a drive in the dry summer weather.
Limited Slip: Also known as Trutrac, performs much like an open rear but when conditions warrant, it transfers some power to the wheel with the MOST traction. This is stock in some vehicles but is also an aftermarket up grade. If you do not go off road, this is a great option.
Posi: Much like a limited slip but both wheels may spin equally... Good for racing and burnouts. Even though both wheels can spin, a posi in NOT a locker and not a good upgrade for a Jeep.
Lunch Box Lockers: Also known as automatic lockers, these are drop in and do not require resetting the ring and pinion ~ much easier to install and less expensive then selectable lockers (below).
Mechanical Locker: A great off road system, but not recommended for street use. This locker used centrifugal force to operate - basically, if you are on the throttle your wheels are locked. This creates major problems on dry roads, especially when installed on the front axle. A mechanical locker is also very noisy as it constantly locks and unlocks. There are several companies that make these with some variations.
Soft Locker: The latest design in automatic lockers. Overall it is a mechanical locker, but it performs quitter and has the ability to automatically allow wheel speed differentiation when required.
No-Slip: This is a new style Limited Slip produced by POWERTRAX®. It works in the same fashion but transfers more of the needed power to the wheel with the most grip.
Selectable Lockers: "Selectable" meaning you as the driver selects when to engage and disengage the lockers. These lockers are an open rear when not in use and a fully locked axle when engaged. These are the best option for those who drive their Jeep to work everyday and take it off road on the weekends.
Cable Locker: "Ox" is the brand name and the only company that produces a cable actuated locker. An Ox shifter is installed inside the Jeep and simply pulled back to engage the locker. The benefit? No wires or air hoses/compressors to worry about. Of course the cable can still get damaged but Ox also has an optional 'Drive-away lock' so you can still engage if needed. A heavy duty differential cover is included with all OX lockers - these are 100% USA made.
Electronic Locker: Eaton makes the original simple to use elocker and they are great on the trail. Once installed, a simple push of a button gets you locked - push it again and you're back to an open rear. The obvious downfall is the wire - it can corrode, short out, get snagged on a branch, etc - as long as it is installed properly and basic maintenance performed, it should give you years of use. The JK model Rubicon's come with an electronic locker produced by GKN and works just like the Eaton brand locker, but a little more complicated and more prone to fail. Many other car companies offer electronic lockers as well.
Air Locker: The Australian based company ARB is the go to brand when it comes to air lockers. An air locker is basically the same an electronic locker but uses pneumatics to engage. The ARB air locker is the choice of many pros and has been tried and proven over and over. The install is the most complicated and overall it is the most costly system. Along with the locker(s) you will need an air compressor installed, the added bonus is you can go with an upgraded compressor to run air tools and air up your tires. There is an air line running under the Jeep and more items that can fail; but again, when installed and maintained properly they will last you years.
Spool Lockers: A spool locker is 100% locked 100% of the time. These are competition/dedicated off road vehicle use only. Many DIY off roaders will weld their spider gears together to create a spooled locker. With a spool installed the axle shafts are prone to break if not upgraded. Yukon makes a great spool produced with high quality 4130 Chromoly steel.