Torsen Differential, How it works ?

Torsen is a trademark of
the JTEKT Corporation.

The Torsen differential has
many patented components

and is the most unique and ingenious
method of providing differential action

while overcoming the traction
difference problem.

The internal components of
a Torsen are quite different

from that of a conventional differential.

At the heart of the system lies
a specially shaped gear pair assembly.

Let's see the cross-sectional shape
of these gears at the mating point.

As can be seen one gear is a spur gear

and the other one is a worm gear.

A Torsen works on the simple principle
of worm gear worm wheel.

That is, a spinning worm gear
can rotate the wheel.

But the rotating wheel cannot
spin the worm gear.

Throughout this discussion just
keep this principle in mind.

A pair of such worm wheels
are fitted with the case.

So the engine power received by the case
is transferred to the worm wheels.

Each end of the wheels
is fitted with a spur gear.

Now let's consider different
driving scenarios.

When the vehicle moves straight,

the worm wheels will push
and turn the worm gears.

So both the drive wheels
will rotate at the same speed.

Please note here that, in this condition,

the worm wheels do not spin on its own axis.

In this condition the whole mechanism
moves as a single solid unit.

When the vehicle is negotiating a right turn

the left wheel needs to rotate at
a higher speed than the right wheel.

This speed differential is perfectly
supported in the Torsen.

The worm gear of the faster left axle

will make the corresponding
worm wheel spin on its own axis.

On the other side, relative to the case,

the slow right axle is turning
in the opposite direction.

Thus the right worm wheel will
spin in the opposite direction.

The meshing spur gears at
the ends of the worm wheel

will make sure that the worm wheels
are spinning at the same speed.

Thus it guarantees a perfect
differential action.

Now let's try to understand how

the Torsen overcomes the drive
wheel traction difference problem.

As you might be aware,

when your vehicle encounters
a situation as shown,

the slippery wheel starts
to spin very rapidly

and will draw the majority
of the engine's power.

As a result the vehicle will get stuck.

But, if a Torsen differential
is used in this case,

as soon as the slippery wheel
starts to spin excessively,

the speed change will be transferred
to the worm wheel.

The right worm wheel transfers
the speed change to the left worm wheel

since they are connected through spur gears.

Here comes the tricky part.

The left side worm wheel will not be able
to turn the corresponding worm gear

because, as we said, a worm wheel
cannot drive a worm gear.

As a result the whole mechanism gets locked

and the left and right wheels turn together.

This allows a large amount of torque to
be transferred to the high traction wheel

and the vehicle can thereby overcome
the traction difference problem.

To carry the load, two more
worm wheel pairs are added.

If you are familiar with the other
common technologies

used to overcome the traction
difference problem,

you might have noticed a great
advantage of the Torsen.

While the other technologies
allow the drive wheel

to slip for a limited amount of
time before it gets locked,

in Torsen, the locking action
is instantaneous.

That means, as soon as the vehicle
encounters a traction difference track,

the wheels will get locked.

To know more about
the clutch pack LSD technology,

please check the next video.

Thank you!