What is a Diff-lock?
What are they and how do you use them?
Diff-locks: what are they and how do you use them?
If you’ve got a 4x2 Hilux or a Prado, or one of the other members of the Toyota 4x4 and bakkie range, you’ve probably got a little button on the dashboard that activates a diff-lock. But just what is a diff-lock?
To answer that question we first need to make sure you understand what a differential is. On each axle are two wheels. When the vehicle drives in a straight line, the wheels turn at the same speed, but when the vehicle goes around a corner the two wheels turn at different speeds, because they travel different distances. To enable this to happen without tyre or vehicle damage, a differential is fitted between the two wheels that allows them to turn at different speeds.
Differentials send power to the wheel that is easiest to turn, which works well on tar. But off-road this is a problem because the wheel that is easiest to turn is the one with the least traction (it might be spinning in mud or even be up in the air).
To solve this, diff-locks or locking differentials are used. As the name suggests, a diff-lock locks the axle so that the two wheels turn at the same speeds.
Here’s an example of when this is useful: you’re driving in muddy conditions and one wheel starts to spin in deep mud while the other wheel is on firm ground. Without a diff-lock, all the axle’s power will go the useless spinning wheel. If you engage the diff-lock, each wheel will get the same amount of power and so the wheel on firm ground will turn and push the vehicle forward.
So far we have discussed a diff-lock on an axle (usually the rear axle although the Land Cruiser 70 series, for example, also has a diff-lock on the front axle) but there are also Toyota vehicles fitted with a central diff-lock, such as the Land Cruiser models. A central diff-lock ensures that power delivery is split equally between front and rear axles.
When to engage the rear diff-lock
- When the ground is rutted and one wheel may leave the ground.
- You’re travelling at low speed and one or more wheels will probably lose traction, such as muddy areas.
When NOT to engage the rear diff-lock
- On tar, or any other surface with good traction.
- When you need to turn tightly – diff-locks increase the tuning circle.
- Any conditions where you will drive quickly, such as sand.
Don’t engage your diff-lock on a tar road or any other surface with very good traction, as this can damage the differential. To avoid this, a good habit to get into is to use your diff-lock only when you need it, and disengage it as soon as you no longer need it. When a diff-lock is engaged, a light will light up on the instrument panel, just to make sure that you don’t activate a diff-lock unintentionally.