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Automatic vs. Selectable Lockers: Which Is Better?

Posted in Features on December 17, 2018
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Photographers: 4 Wheel & Off-Road Staff

While not quite as polarizing as the Chevy versus Ford argument, there’s rarely a lack of opinion among off-roaders when it comes to the question of automatic versus selectable lockers. Not sure what the difference is? With a selectable locker, the driver can control whether or not the differential in an axle acts like regular open diff (enabling the tires to turn at different speeds but also allowing engine torque to take the path of least resistance), or locked together so that both tires receive engine torque equally regardless of traction. Selectable lockers can be operated by air, electricity, or even levers and cables depending on the brand. An automatic locker mechanically locks both tires on an axle together when under power, but also has a torque-sensing function that will unlock one tire and allow it to spin faster than the other when coasting (such as when going around a corner). Put another way, an automatic locker allows one tire to rotate faster than the other, but never slower. While both types of lockers do the same thing, one does it automatically and the other gives locking control to the driver. Our intrepid group has spent lots of time with both types of lockers, and not surprisingly, preferences for either type differ among them for a variety of reasons and types of terrain. Is one locker a clear winner? Read on and decide for yourself.

Selectable lockers have switches mounted somewhere on the dash that allow the driver to turn a locker on or off in an instant. There are many kinds, but the most common are activated by either air or electrically. In both cases, there are a variety of components involved in locker controls, which means ample opportunity for failure.

Verne Simons

Technical Editor
This is a fairly easy decision for me. I think. Maybe not. I greatly prefer the idea anyways, of a selectable locker for at least one “good” reason. This reason revolves around my opinion that automatic lockers (and lockers in general) make all of us lazy drivers. Open diffs are everywhere, and it’s amazing how far you can get down the trail with an open locker if you actually think about where and how you are going to place the rig and the tires. Automatic lockers are great because they give reliable traction always. There’s no forgetting to flip a switch, no wiring or airlines to worry about, just traction. But in my mind there is no doubt lockers (and automatic lockers especially) make you (me) a more lazy driver.

Part of why I like off-roading is to test and hone my driving skills. With a selectable locker you can choose to have the traction (if you’re tired or have a real reason to make the obstacle on the first try), or you can test your driving skills with the differential(s) unlocked. Of course, it’s easy to make the counterargument that an automatic locker is easier on parts while on the trail since you generally can use less speed and more finesse with both tires per axle spinning. On the other hand, selectable lockers have much better street manners and are easier on parts while on the asphalt. To some extent, the question boils down to, “What do you want from the vehicle in question?” Truth is I have vehicles with both automatic and selectable lockers and I like them both.

Both types of lockers commonly require a complete replacement carrier, which means checking and often adjusting the ring-and-pinion setup. A couple of automatic versions drop into an existing carrier, making installation cheap and easy, but this can come at the expense of strength. Installing a selectable locker requires the added steps of drilling a hole in the differential housing and plumbing or wiring to dash-mounted controls.

Harry Wagner

This argument often gets derailed into a discussion about strength, but to me it is more about reliability. There is no question that selectable lockers are strong and offer features that can’t be matched by auto lockers. Selectable lockers can be turned off on the street to eliminate any handling quirks and help your expensive tires last longer, making them the easy choice for a daily driver. They are far superior on slick and icy roads, where you want only one tire per axle providing power to move forward and the other tire to act as a sort of rudder. And on the trail, you can leave selectable lockers off to reduce strain on axle and steering components. I even built my Tracker with cutting brakes on the rear axle to provide better maneuverability with the rearend unlocked.

So I am all about selectable lockers, right? I am on my daily driven vehicles, but none of those benefits particularly matter to me when I am on the trail and an air line, or a solenoid, or a seal fails. Do they increase my turning radius? Yes. Do you have to alter your driving style to account for them on the street? Yes, particularly if you don’t have much air in your tires. Auto lockers are stupid simple, which is why I run them in the front and rear of my Ford and my Toyota.

Automatic lockers utilize a clever design that senses torque input and will unlock one ale to allow one tire to spin faster than another when coasting. The moment you step on the throttle, however, they immediately lock the axles together. This causes some handling quirks on the street that can make them tiresome on a daily driver.

Trent McGee

Nuts and Bolts author
While I really like selectable lockers on a daily driver, I find myself firmly in the automatic locker camp. Like some of the other guys, to me the deciding factors are reliability and ease of operation. There are lots of components associated with a selectable locker, and therefore ample opportunity for failure. I can’t tell you how many times I’ve seen selectable locker failures on the trail, but it’s extremely common. Whether it’s a sticky solenoid, a broken air line, a popped fuse, or a broken wire, it happens all the time. The failures are usually minor, but they’re persistent and annoying.

It’s rare to see an automatic locker not working, and if you do it’s usually because something very bad has happened. Equally common is drivers forgetting to turn one or both lockers on, which causes delays, confusion, and often frustration for everyone. Sometimes you only get one shot on an obstacle, and you waste it if you forget to turn the lockers on. If I’m in a rig with selectable lockers, I usually end up leaving the rear one on after the first obstacle and only turn the front one on and off, and half the time I forget to turn it on when I need it. And thus the cycle repeats. With an automatic locker you don’t have to think about it, so it’s one less thing to forget. I’ve driven locked rigs for so long now I don’t even notice the driving quirks of automatic lockers anymore, and you can alleviate most of the increased turning radius with a little planning and a twin-stick transfer case.

With all of that said, I currently own my first rig with selectable both front and rear, and I love it. But I don’t love that I’ve already replaced a compressor and a solenoid, and currently have another solenoid that is drooling gear oil in the engine compartment. Which in turn further solidifies my opinion on the subject.

Both types of lockers can be extremely effective in virtually any types of terrain. The one limitation of a selectable locker, though, is human error: They only work when you remember to turn them on. With an automatic locker, you never have to worry about having maximum available traction at all times.

Christian Hazel

For starters, I’ll take a spool over an automatic locker in the rear of a vehicle any day. I just find them more consistent, with no unwanted banging and clanging. If I have an automatic transmission I prefer not to have an auto locker up front. I’ve found with a manual I can modulate the throttle and/or clutch in such a way that I can freespool a front auto locker and gain a bit of turning radius in hardcore technical work. And while I do enjoy the simplicity of an auto locker/spool combo, lately I’ve been running selectable lockers in most of my builds, like the UACJ-6D. Not only does a selectable locker allow you the utmost in turning radius and streetable manners, but it also allows you to engage the locker only when you need it, thereby minimizing the chances of an axleshaft or U-joint failure. The downside is you need to remember to turn them on, because more than once I’ve entered into a make-or-break obstacle with no chance of backing out of only to fail and have to winch because I forgot to engage my lockers. D’oh. I guess I’d better stick to the auto lockers after all.

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