What does a center locking differential do? | all about differential locks made easy - Off Roading Pal (2023)

The center differential lock gives you the ability to lock both the front and rear axles to evenly split engine power (torque and RPM) between the front and rear wheels.

This may be a bit confusing for you. But no worry. I will explain in the simplest possible way why these things are important and when to use them. In this guide, I'll talk about a general mechanism to keep things simple and clear.

What is a normal rear axle differential used for?

Imagine a car going straight on a freeway. If all the wheels are spinning in a straight line, the speed of rotation of all 4 wheels is the same.

But when you are in a corner (taking a corner) things change. 4 wheels take 4 different paths. You can see it in the video below.

What does that mean? This means that 4 wheels cover 4 slightly different distances in one unit of time. It just means that the rotation speed of the wheels is different.

Let's just take the 2 rear wheels. The wheel on the inside (near the middle of the arc) of the curve should spin slower than the outside wheel. Otherwise, the cars won't make it through the curve.

How is this wheel speed difference achieved by a car? Because of its differential, which locates the center of two rear wheels.

So the purpose of the differential is to spin the two wheels at different speeds when needed.

This is done by a mechanism in the differential, performed by a system of sprockets and three axles.

The simple differential lock is a type of lock that stops the normal mechanism of a differential, allowing the right and left wheels to rotate at the same speed.

What is the difference between 4WD and AWD?

To explain this simply, I drew the following simple diagram.

Both AWD and 4WD, according to the diagrams, transfer power from the engine to the transmission unit through the clutch or torque converter, depending on whether it's a manual or automatic transmission.

Then the difference happens. AWD has a center differential. Through this power transmission to the front and rear differentials and through these differentials to all four wheels.

There is another clutch between the center and rear differentials to transfer more torque in that direction when needed.

But it is not very important for our discussion now.

But in 4WD there is a transfer case. The transfer case is the unit that splits engine power between the front and rear wheels 50/50 when all-wheel drive mode is engaged.

When 4WD mode is off, it sends 100% of the engine's power to the rear wheels.

Through the transfer case, power goes to the front and rear differentials and then to all four wheels.

Such are the differences of the mechanisms in the AWD and 4WD systems.

What is a center differential lock for?

This central diff lock also performs the same job as normal diff locks.

It locks the normal differential mechanism and allows for an even distribution of power to the front and rear axles.

What does that mean? Let's take an example.

When is the center differential lock used?

Consider that both front wheels of an AWD vehicle are stuck in snow and the rear wheels are on hard pavement.

If the center differential disengages and you try to reverse the vehicle to get what happens.

The open center differential on AWD vehicles is always trying to send power to the wheel that spins easily.

In this scenario, these are the front differentials. It sends all the power to the front wheels, and the front wheels spin continuously.

No rear wheel spin. The vehicle doesn't move an inch.

Then the center diff-lock kicked in and tried to reset again. So what's up. The center differential is now locked.

In this way, the power is evenly distributed and transmitted to the front and rear differentials.

The front wheels still spin, but the rear wheels get the job done on rough roads. The vehicle can drive out of the stuck spot.

But remember that this is just an example to explain this. But modern AWD vehicles are equipped with computer units and traction control systems.

They manage to transfer the engine torque to the wheels with more traction. If you're curious whether locking the center differential or locking the front and rear differentials is better for off-road use, you can read about it herethis guide.

For 4x4 vehicles

On 4x4 vehicles, when you activate 4x4 mode, it simply acts as a central differential lock from the transfer case.

This means, as I mentioned earlier, that the transfer case splits engine power 50/50 front and rear, similar to when AWD is engaged in the center differential lock.

I think you've nailed it now.

Important things to know when activating 4x4 mode.

By now you know how it works. So consider an example of a four wheel drive vehicle in 4x4 mode on a highway. What can happen.

Let's go to the beginning. As I mentioned before, when a car turns, all 4 wheels spin at 4 different speeds.

When 4-wheel mode is engaged, it means the transfer case is trying to turn the front and rear axles at the same speed.

But that can't happen in curves. In this case, it causes damage to the transfer case, gears and drive shafts.

For this reason, it is recommended to only activate 4x4 mode when necessary, e.g. B. in the field. On roads, you can engage 4WD mode when you really need it, but at somewhat slow speeds.

But now there are new vehicles that can drive on roads at high speed by making changes to the previous general mechanism.

For example, adding a coupling system (visco coupling) between the transfer case and the rear differential solves the problem. Provides the ability to rotate the front and rear drivetrain axles at different speeds if needed.

Do you think your vehicle's traction control system will help you when you're driving in the mud? I wrote a separate article about this.

If you are interested, you can read that too. to read thatClick here.

So things are changing fast. But the basic mechanics should be in your head to understand these things.

So I think I've covered all the things I mentioned at the beginning.