Thread: Diff locks and traction control

I probably should have put the question like this

My 04 D2A has TC and CDL factory built in

If I fit an aftermarket rear diff lock will there be an issue

I think by reading all the feedback , the answer is no , there won't be

As someone said , Rear locker in , should be no rear wheel slip , TC not needed

Front wheels slip, TC comes on

Originally Posted by land864

I probably should have put the question like this

My 04 D2A has TC and CDL factory built in

If I fit an aftermarket rear diff lock will there be an issue

I think by reading all the feedback , the answer is no , there won't be

As someone said , Rear locker in , should be no rear wheel slip , TC not needed

Front wheels slip, TC comes on

The answer is no you will not have issues .
And your explanation is correcto

Originally Posted by land864

....

As someone said , Rear locker in , should be no rear wheel slip , TC not needed

Front wheels slip, TC comes on

The routine to have in mind would be:

CDL engaged(less likelyhood for a front wheel to spin), rear diff lock engaged (if you think the situation calls for it).
But if one of the fronts does try to spin, the TC then controls it.

Originally Posted by land864

Front wheels slip, TC comes on

In the case of both wheels slipping, yes TC will come on.

But it wouldn't be possible to spin a single wheel in this setup, and without spin the TC doesn't activate.

The main issue with the rear locker // locked cdl is that if you lose traction on one front wheel you get very limited power to the front wheel with grip.
This is because an open diff splits torque 50:50 and is limited to the amount of torque that can be applied to the wheel with least grip.

In other words you turn the D2 into a rear-wheel drive only truck when a single front wheel loses traction.

But at least you can say you have a rear locker fitted...

Add:
These are plots of wheel speed and torque at the wheel done in Simscape Driveline.
The setup is a 4 wheel drive drive train with centre diff and rear locker simulated with a dog clutch.
The front diff is one of the default open differentials.
The two rear wheels and right front are on models of dry asphalt, while the left front is on a ice model with the grip reduced to simulate a wheel in the air...

First plot shows wheel speed is identical on all wheels...

wheel_speed.jpg

While there is almost zero torque on both front wheels, with torque redirected to the rear wheels.

wheel_torque.jpg

Originally Posted by OffTrack

In the case of both wheels slipping, yes TC will come on.

But it wouldn't be possible to spin a single wheel in this setup, and without spin the TC doesn't activate.

The main issue with the rear locker // locked cdl is that if you lose traction on one front wheel you get very limited power to the front wheel with grip.
This is because an open diff splits torque 50:50 and is limited to the amount of torque that can be applied to the wheel with least grip.

In other words you turn the D2 into a rear-wheel drive only truck when a single front wheel loses traction.

But at least you can say you have a rear locker fitted...

Please explain that better cos i'm stumped....
1. why it's impossible to spin a single wheel in this setup?
2. wouldn't the front diff engage if the TC puts brake on the slipping wheel?

An open diff does not split torque 50:50. A locked diff does. It would be entirely possible to spin a single wheel with a locked rear and open front

Originally Posted by OffTrack

In the case of both wheels slipping, yes TC will come on.

But it wouldn't be possible to spin a single wheel in this setup, and without spin the TC doesn't activate.

The main issue with the rear locker // locked cdl is that if you lose traction on one front wheel you get very limited power to the front wheel with grip.
This is because an open diff splits torque 50:50 and is limited to the amount of torque that can be applied to the wheel with least grip.

In other words you turn the D2 into a rear-wheel drive only truck when a single front wheel loses traction.

But at least you can say you have a rear locker fitted...

Read what you wrote, veeeerrryyyyy slowly.

Originally Posted by Disco Muppet

An open diff does not split torque 50:50. A locked diff does. It would be entirely possible to spin a single wheel with a locked rear and open front

That is a common misconception.

A locker fixes the output speed at 50:50 of the input speed. But torque bias ratio can be up to 0:100 if one wheel has no grip.
An open diff splits torque at 50:50, but allows output speed to vary up to 0:100.