Thread: Torque Biasing Diffs

Originally Posted by workingonit

I get the impression load rather than rotational speed is important. The Ashcroft article goes on to say -

The disadvantage of ATB is that if one wheel is totally off the ground ,i.e. no drive then the other wheel similarly because the bias ratio is still 2:1 i.e. 2 x nothing is still nothing. Attempts at changing the preload or left foot braking can then fool the ATB into working or better still if the vehicle is fitted with ATC (automatic traction control) the ATB will enhance the action.

The video clip of the ATB still left me wondering about the physics involved.

I stand corrected on that point.

Chook, have a read of this....

DEFENDER2.NET - View topic - ATB (torsen) front and rear install

In particular...

To get the mostly found misunderstandings out of the way:
- a Detroit locker is not a torsen diff , it is an un-locker
- torsen, which is a LSD as it is not a full locker, has nothing in common with the classic friction plate based LSD’s which operate rotation speed based

I tend to categorize them in corrective and preventive aids.
Friction plate LSD and TC are corrective aids; they react once traction is lost
Full lockers are both preventive and corrective, depending on when you switch them on. But they are a passive system as they need to be switched on.
ATB’s are preventive, they transfer torque before and during loss of traction.

The main catch between both is that the first 2 are taking power, by slip or braking; so they work against the power you put into it, to regain traction.
The ATB’s do not. They transfer the power without consuming or braking it.

Originally Posted by Disco Muppet

Chook, have a read of this....

DEFENDER2.NET - View topic - ATB (torsen) front and rear install

In particular...

Clearly Dave Ashcroft is wrong then.....

I think simply put, a Torsten diff works because its using worm gears, not open gears.. With a little load, these gears are pushed outwards causing drag hence pushing a percentage of the drive to the wheel that's still on the ground. Traction control or left foot braking helps this, but I also found that on my off road vehicle throttle bursts used to have enough effect to get the stationary wheel spinning. With a Detroit in the rear, there's usually a certain amount of forward motion... Add to that a percentage of drive from the front wheel that's still on the ground, gives enough to keep going!!