[ZDan]

Originally Posted by Suberman

A torque biasing differential(ATB) is an open differential.

It comes down to semantics, but for me, no, it is a limited slip differential.

It uses internal friction forces acting on the gear faces and thrust washers to force torque across the differential. It does not limit slip, it transfers torque that would otherwise be wasted spinning a drive wheel.

The ultimate effect of this being: limiting slip of the wheel that wants to spin.

However, it only transfers unused torque.

"ONLY"?! Reminds me of Homer Simpson bargaining with the nerdy science guy over a matter trasporting device: "Hmm, $3, and it only transports MATTER?"

If the lower grip wheel has no grip, there's no torque to transfer.

But the frictional resistance in the worm gears will still transfer drive torque to the non-spinning wheel. I have never had either of my Torsen-equipped cars give a 1-wheel spin on snow or even ice. There is effective rear lockup even with very very very low-traction/low-torque conditions, at least in my experience with them.

Its important to remember that torque is an unmoving force.

"Unmoving"? Of course applying torque can and usually does produce motion.

Only if the lower grip wheel offers resistance to applied torque can that torque be transferred to the other drive wheel. The beauty of a Torsen is you don't get single wheel spin at all until the torque transferred to the other drive wheel exceeds the grip available to that wheel, divided by the bias ratio (or, if you prefer, the low grip wheel will also spin the higher grip wheel when the bias ratio is exceeded, in our cars by four times). In that sense it prevents wheel slip and does not "limit" wheel slip.

Semantics. If it's preventing slip from happening at all, in my book that is LIMITING slip.

It is not a reactive system like a clutchpack or viscous coupling is.

It is reactive, providing more lockup with increased torque, unlike some clutchpack diffs, but similar to a Salisbury (with ramps to increase lockup with increased applied torque) clutch type with low breakaway torque.

It mimics a LSD only if each wheel has some grip otherwise it acts as the open differential it is.

In my experience with Torsen diffs, as long as both wheels are on the ground it will lock up enough to maximize drive even in snow and ice.

A clutch type LSD absorbs engine torque that would otherwise spin the lower friction drive wheel. An LSD does not transfer any torque,

WHAT?! A "mechanical" clutch type diff absolutely DOES transfer torque. It doesn't just "absorb" it. Torque that would act to spin the inside wheel in cornering is transferred through the clutch pack to the loaded outside wheel.

it absorbs engine energy and creates a lot of heat until it locks up.

SOME of the energy is converted into heat in the clutch pack, but a significant amount of it IS transferred as torque to the wheel with grip. Otherwise you'd just feel a big LUG and the car wouldnt' accelerate any more than it would with an open diff, if ALL was lost as heat. Plus you'd vaporize the differntial fluid and melt the diff in short order...

An ATB is not a LSD it is an open diff.

In my book, it absolutely is a limited slip, in theory and in practice. I've driven torsens and Salisbury clutch diffs, and their characteristics aren't too dissimilar. Both can provide adequate lockup without being too obtrusive at low-speed low-torque.

Now you don't need to google Torsen.

I *highly* recommend that people do their own research and not take mine or anybody else's word for it!