Tech Corner: What’s the Big Diff? Why Serious Off-Roaders Choose Air Lockers

Pro Comp Tire A/T Sport

It’s a perfect crisp Fall day. The sun is shining and your 4×4 is blasting through puddles like a dog does right after a rain storm. Suddenly, you hit a hill that you can’t quite clear. One tire spins in the air while another desperately tries to gain traction and you flounder like a sad little beetle stuck on its back. You could have saved yourself a lot of aggravation (and embarrassment) if you had installed a set of solid air lockers.

The off-road market is saturated with useful upgrades left and right. Sure, you can invest in the best recovery gear on the market but first, try taking a look at the differential equipment available today. With the proper setup, there’s a good chance you can get out of a sticky situation without the need of a winch or your buddy’s tow.

The Basics

If you already upgraded your stock open differential to aftermarket air lockers, then we know you can feel the difference. Having the right differential is critical when approaching obstacles on the trail like slippery mud or even sand dunes. And understanding the science behind them, the different styles available, and the best manufacturers on the market can mean the difference between a fun off-road challenge and an expensive break down.

You probably already have some basic understanding of what purpose the differential serves. But just in case you’re due for a refresher, let’s quickly break it down. Called such because it drives the wheels at “different” speeds, the differential simply allows one wheel to drive faster than the other. This is the basic technology that keeps your car from slipping and sliding during turns. If the wheels didn’t turn at different rates, you’d lose traction, which can be very dangerous.

Open Differentials

The simplest kind of differential, an open differential, sends the same amount of torque to each wheel. This is fine when both wheels have traction—like driving on pavement. But in a situation where one wheel has traction and the other doesn’t… trouble. This is because, as an open differential sends the same amount of torque, the engine power follows the path of least resistance and heads straight to the wheel with the least traction. Like in our example above, this is how you end up with one wheel maintaining tire contact while the other spins in the air like a useless pinwheel.

Open diffs are generally inexpensive and require little maintenance, but the resistance they are avoiding translates to traction. So off-road, this means a slipping tire will continue to slip because it’s unnecessarily receiving all the power. Effective for street vehicles but in any case where real traction is needed, they can be pretty useless.

Limited Slip Differentials

This “slipping” that the tire experiences can be somewhat corrected through a limited slip differential (LSD). In fact, most trucks today are equipped with these. And while LSDs solve some problems posed by open diffs, they can still present challenges off-road. When driving with ideal traction, both wheels receive equal torque. But when loose gravel or slick mud presents itself on the trail, an LSD is designed to send more power to the tire with the most amount of resistance–therefore “limiting” the slip. So when you’re sitting with one tire in the mud and another on a rock, the tire on the rock will get more power because it has more traction.

These units are useful, but they are still sending an uneven amount of power to the wheels. As a serious off-roader, you’ll want more control than a limited slip can give. And this leads us to why you should consider air lockers.

The Power of Air Lockers

Locking up a differential is no new trick. In fact, you’ve probably got a buddy with a Cherokee he’s Lincoln locked at home. Locked up differentials ensure that both wheels will constantly receive full power regardless of resistance. The problem with a permanently locked differential is that street use is totally impaired because the truck will eat through tires and be hard to control when turning.

Air lockers, by design, allow one to easily lock up a differential on command. This means both tires will receive torque only when needed. Having this unit on board is perfect for those who do some hardcore off roading on the weekends but daily commuting throughout the week.

ARB Air Lockers Take You Farther Off Road

ARB is a known industry leader providing off-road enthusiasts with quality air lockers. “The advantage of the ARB Air Locker lies in the pneumatically-operated locking system inside the differential. When activated, the air locker prevents the differential gears from rotating and therefore prevents the axle shafts from turning independently of each other. With both wheels tied directly to the rotation of the ring gear, the vehicle maintains maximum possible traction at all times. When unlocked, it operates just like a conventional ‘open’ differential,” explains the company.

With air locker kits, like those offered by ARB, the driver has the power to lock up the differential on command right from the driver’s seat. This means that as you transition into a certain environment, you can simply switch the locker to engage, and then switch it back as you leave the trail. The use of a pneumatic-based system makes for a reliable operation and a positive engagement—meaning once that switch is flipped, there’s no guessing what the wheels are going to do.

Air lockers are extremely convenient for those looking to boost off-road performance. And, “in addition to providing outright improvements to a 4×4’s off road capabilities, the air locker offers significant environmental benefits. An air locker equipped vehicle can be driven in a slower, safer, and more controlled manner. This greatly reduces the likelihood of vehicle damage and environmental impact,” says ARB.

Not a Small Investment

An air locker kit uses a differential carrier combined with a compact air compressor for operation. This means the unit will work independently on all on-board systems, aside from its source of electricity. Altogether, you’re looking at a retail of roughly $1,000 for a single carrier and another $500 for the compressor. One compressor can operate two air lockers from ARB. So, if you intend on converting both differentials on your rig, the air locker kit will run about $2,500.

This price doesn’t include labor of installation or the cost of other essential materials like gaskets, bearings, and gear oil. And unless you have a high understanding of working with differentials, you’ll want to have these kits professionally installed. This is a specialized installation requiring specialized tools.

Remember that while engaging the air lockers is simple, knowing how to properly use them takes patience and skill. Follow the operating instructions and take care of your investment. Winter is steadily approaching. Just as you replace the regular fluids in your car, your differential oil needs to be maintained and flushed of any trapped water. Obviously, this is no small purchase. But if you are serious about off-roading and want to take advantage of everything your vehicle has to offer, it’s definitely something to consider.

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