Locking rear differentials explained: How a simple button could save your 4x4 adventure
The game-changing off-road tech that keeps you moving when the going gets toughOff-road adventures are full of surprises, loose sand, muddy ruts, rocky climbs. And when one of your wheels loses traction, you could easily find yourself stuck, with one tyre spinning helplessly while the other stays still.
That’s where locking differentials, or diff locks, come into play—especially the rear diff lock, which is one of the most common and useful features in today’s 4x4 utes and SUVs.
But what exactly is a locking differential? How does it work? And when should you actually use it? Let’s break it down.
What happens when traction disappears?
Most vehicles have open differentials, which allow the left and right wheels to spin at different speeds. This is essential when turning on sealed roads—the outside wheel needs to rotate more than the inside one to make the turn smooth and stable.
However, off-road this can become a problem. If one of your wheels lifts off the ground or hits a patch of slippery mud, the diff will send most (or all) of the power to the path of least resistance—the wheel with no grip. You’ll be stuck spinning one tyre while the other sits idle.
What does a diff lock do?
A locking differential overrides this behaviour, forcing both wheels on the same axle to spin at the same speed, even if one is in the air or bogged down.
That means the wheel with traction still gets power, which can help your vehicle keep moving, climb obstacles, or pull itself free from sand or mud.
Rear diff locks in modern 4x4s
Many modern off-roaders—including vehicles like the Mazda BT-50, Ford Ranger, and GWM Tank 300—now come equipped with rear diff locks. Some even offer front and centre locking diffs, although these are typically found on more serious off-roaders.
In the BT-50, for example, engaging the rear diff lock is as simple as pressing a button. You’ll need to select low-range 4WD (4L) first, which usually requires putting the vehicle in neutral. Once you’re in low range, the rear diff lock can be activated at speeds up to around 8km/h. A dashboard light confirms it’s engaged.
Newer models like this Mazda also allow the front traction control system to remain active while the rear diff is locked. Something that wasn’t always possible in older 4x4s.
When to use a rear diff lock
A diff lock isn’t something you leave on all the time, it’s a tool for specific situations. You should:
- Engage it before you get stuck, especially when approaching steep climbs, deep ruts, or loose surfaces like sand dunes
- Use it only at low speeds—generally below 10km/h
- Disengage it before returning to sealed roads, as it makes turning difficult and can stress the drivetrain
If you try using a rear diff lock on hard surfaces or while cornering at higher speeds, you’ll feel resistance and strain in the drivetrain. That’s your car telling you it’s not happy.
A rear diff lock is one of the simplest yet most effective tools for off-road driving. It won’t make your 4x4 invincible, but it can be the difference between making it through a rough section or having to call for help.
Related: A step-by-step guide to using recovery tracks for off-roading
Related: Top five sand driving tips
Related: What you need to know about 4x4 traction control
Please see our Editorial Guidelines & Code of Ethics (including for more information about sponsored content and paid events). The information published on this website is of a general nature only and doesn’t consider your particular circumstances or needs.
