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So You Want to Lock Your Vehicle

And no I don’t mean locking your doors, tail gates or Tuffy boxes. What we are talking about here is adding traction devices to your vehicle’s differential(s) called lockers.

Before we get into a discussion as to what they are and why you might want them, lets talk a little bit about traction. Traction is simply getting the power from your engine to the ground. The only thing that is supposed to contact the ground is the tires, which is the number one traction device.
When you have the vehicle in 4-wheel drive, the transfer case splits the power, driving the front wheels as well as the rear wheels. You now have 4-wheel drive, or do you really.

Since most vehicles have what they call open differentials, the vehicle has 4 wheels pulling as long as all 4 wheels are on the ground and are on the same type of surface. Obviously if one wheel is off the ground, that tire is not providing any traction. What most people don’t realize is that with stock open differentials, not only is the tire off the ground not providing any traction, neither is the other tire on the same axle. To allow for smooth cornering, one wheel must be able to turn slower or faster than the other. With an open differential this is done with spider gears which diverts power to the outside wheel in a turn allowing the inner wheel to turn slower than the outside wheel. The downside to this method is that when one tire is in the air, or on a slick surface such as ice, all the power is diverted to the tire with no or little traction. If you ever watch a jeep with one front tire off the ground, you will see that the tire in the air is turning, but the one on the ground isn’t. The Jeep just went from 4 wheel drive to 2 wheel drive. Now imagine what would happen if you got into a situation where one front tire was off the ground and one rear tire came off the ground. You just went to no wheel drive as the 2 spinning wheels are putting no power to the ground. This may sound improbable, or even impossible, but it happens all the time in rough terrain.

To lessen this problem most vehicle manufactures offer limited slip differentials, also known as posi traction. Instead of spider gears, the deferential has a traction aiding device, usually with clutches, which provides some power to the wheel with more traction. It allows some slip which is needed when cornering, and helps when one tire is in mud and the other on solid ground. The problem with limited slip is that when one tire totally loses traction, such as when it is in the air. All the power goes to the wheel in the air and none to the wheel still on the ground. Some limited slip’s are better than others, but none is as good as a locker.
Ok, so what is a locker and do I want one.

A locker is a device that is put in your rear and/or front differential which causes both wheels to receive power from the engine regardless of which wheel has more traction. A locker replaces the spider gears and sometimes the carrier as well. There are 3 basic types of lockers, only 2 of which are suitable for both on and off road driving. There is a permanent type locking device called a spool where by both the left and right axles are permanently locked together. While this may be suited for drag racing, or off road driving on soft surfaces, it is totally unsuited for on road driving as there is no provision for cornering where the wheels need to turn at different speeds.

The second type of locker is the manual locker, such as the after market ARB Air Locker, or Toyota’s electric locker. These lockers are turned on and off manually, and have the advantage of having no side affects when turned off and the vehicle is driven on the road. When the locker is turned on, both wheels are locked together just like a spool. Manual lockers are the most expensive as the ARB has a price of about $600.00 and requires an air compressor which costs another $185.00. Since the ARB locker replaces both the spider gears and the carrier, the ring and pinion will need to be set up again, which will cost about $250.00. If installed in both the front and rear, the cost will almost double.(You will not have to buy a 2nd air compressor) As far as I know the ARB Air Locker is the only readily available after market manual locker for a wide variety of applications. Their only, drawback, other than being quite pricey, is that they are prone to air leaks and can refuse to lock at the most inopportune time.

The third type of locker is the automatic locker, and is probably the most common for off road use. Some of the automatic lockers, like the Lock Right or Detroit EZ Locker, just replace the spider gears, while some like the original Detroit Locker replaces both the spider gears and carrier. The Lock Right locker can be usually had for less than $300 and does not require that the ring and pinion gear be set up again. To have the Lock Right installed will cost around $100.00, but is usually not that difficult to install if you have slightly better than average mechanical ability. Here's the install instructions for one brand of auto locker. Aussie Lockers. The Detroit Locker or other automatic locker which replaces the carrier will cost between $400.00 and $500.00, and will cost more to install, around $250.00, because of the ring and pinion set up that is required. Setting the ring and pinion is something best left to professionals.

The automatic locker works by not letting one wheel turn slower than the wheel receiving power. This means that when the vehicle is in a turn the inside wheel, or slower turning wheel is receiving power. The outside wheel unlocks and is allowed to turn faster, but without power, than the inside wheel. When the turn is completed and the outside wheel slows down and matches the speed of the powered wheel it locks and also receives power. This is just the opposite of an open differential, where one wheel is allowed to turn slower than the wheel receiving power. Because of this an automatic locker can be a little jerky in turns and in acceleration as the wheels lock and unlock It takes some getting used to and you have to be a little more careful under slick or icy road conditions Automatic lockers also tend to be noisy.

Automatic lockers for the front end are not recommended if you plan to use 4-wheel drive on icy roads. It is for this reason that many individuals put a manual locker or a limited slip in the front end and an automatic locker in the rear.

If you are going to install only one locker, it is usually installed in the rear, because when climbing hills most of the weight is shifted to the rear wheels.

While lockers do add quite a bit of traction off road, there are some drawbacks. The vehicle is harder to steer and tends to want to slide down hill in slick off camber conditions when the locker is engaged.

Lockers also require a slightly different driving style. Because of the increased traction, less power and speed is needed in most instances. With lockers overly aggressive driving usually breaks things.

Do you need lockers? For the trails we normally ride the answer is no, as open or limited slip vehicles do well on our trails.

Now if you ask yourself if you want lockers, that’s a different question. To go where no rig has gone before. To be a man amongst men. You get the picture.