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When Do You Lock Your Jeep’s Axles?

Posted in Features on June 5, 2018
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Ever since the introduction of the Rubicon model in 2003, the axle lock feature or “locker” has been a mainstream feature for anyone who walked onto a Jeep dealer lot. The continued growth in sales of Rubicon-model Jeep Wranglers (new and secondhand) will mean more new owners on the trails who may not fully understand when and where to best use the electronically activated lockers in the front and rear axles of the Rubicon model. Even for the experienced, a refresher and examination of our own thinking can be helpful.

The Basics

Let’s start with the basics. In a vehicle with open differentials the power flows at different rates to the wheels on each side of an axle, which allows the vehicle to turn corners smoothly. The power goes to the wheel with the least resistance. This is a good thing for street driving, but can cause difficulty on the uneven terrain of 4WD roads. Since the power goes to the wheel with the least resistance, this means that the tire with the least traction is getting the power, and breaks loose and spins.

Rubicon axle lock switches have migrated around the dashboard over the years, but the JL finally separated the engage button from the disengage/off button.

Many vehicles come with enhanced traction devices such as limited-slip differentials and electronic traction control systems, but these are not to be confused with full differential lockers. When engaged, differential lockers apply power equally to both wheels on an axle, regardless of how much resistance exists at each wheel. This helps the vehicle to have full traction available at both wheels on the axle. It can, however, limit the vehicle’s ability to turn.

There are two different types of differential lockers, automatic and selectable. Many of us “old schoolers” ran (or still run) what are called full-time lockers, aka Detroit lockers or automatic (pneumatic, electric, mechanical) lockers. These are not actually engaged full time, as the misnomer implies, but only engage when throttle is applied. When you let off the throttle, the locker disengages, and you can once again turn corners.

When a tire comes off the ground, it has no resistance and will be the one to spin, unless the locker is engaged.

Driving Behavior

The factory Rubicon lockers are an electric selectable locker, which has the advantage of being able to engage or disengage with the push of a button. The main difference between a selectable locker and an automatic locker is in driving characteristics. While an automatic locker will release when you let off the throttle, a selectable locker stays engaged until you push the button to turn it off. That subtle difference can mean a lot when you’re on a tight or steep or slippery trail.

In my opinion, a Rubicon, or any other vehicle with a selectable locker, works best when the locker is actuated or “turned on” for the few feet on the trail when you need it. When it is actuated, you are driving with full hard differential lock the whole time, not just when you are pressing the throttle. Turning corners is difficult and hard on the vehicle, even on dirt. Street driving is out of the question. It’s not to be used for the entire duration of the trail—only when needed.

The question of when to use lockers or not (and it’s usually best done just before, as opposed to in the middle of, the challenging sections if at all possible) will be more easily answered with increased seat time in your Jeep. In either case, if the lockers are engaged and the Jeep is bouncing, spinning tires, and hopping up and down like an angry mule, you are in imminent danger of snapping an axle.

Lockers are awesome tools, but misunderstanding and misuse of the axle lock feature can be expensive. It’s a pay-to-play sport. The harder you play, the more strain your axles, steering, and drivetrain experience. But, it’s worth it.

Having lockers engaged on a steep, loose, slippery, and off-camber climb can make the difference between making it and not making it. It also makes the power application predictable to the driver, whereas wheel power differentiation would make this climb even more uncertain.
The JLs don’t even use the term “axle lock” anymore, but have replaced it with little lock symbols throughout. We like that the dash shows the center lock, indicating that power to front and rear axles is locked at an even 50/50 split. This feature is called “locker” or “center diff lock” by the Land Rover and Toyota world, nomenclature that causes much confusion between species.
When you have lockers on and are literally up against a rock and a hard place, use the throttle very gently. You don’t want a shock load delivered through the drivetrain when there is that much force trying to stop the wheels from moving at all.
Using your lockers when coasting downhill only makes the vehicle harder to steer.
After we explain to clients about using the axle lock and sway bar button on JKs, some also ask, “But when do I push the Off-Road button?” Maybe not the greatest design choice ever?

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