[ZDan]

Originally Posted by Gforce

Now there are two posters who seem not to understand how different a Torsen is.

Well, there's at least one!

Clutch type LSD react only to wheel speed, that's how they engage.

Viscous and Gerotor types react to wheelspeed, but not the clutch type.

Clutch type will have some breakaway torque, so it's already locked to some degree before anything even happens. The clutch type then locks up more with applied torque. Even a "plain" clutch-type without ramps does this due to the spider gears being forced apart harder with increased torque at the carrier, which increases clamping force on the clutch pack. A Salisbury clutch type will do this to a greater degree and is tunable with ramp angles.

So without any wheel motion (in unison or differential), the clutch-type already has some lock, and with torque applied it has even more lock.

Clutch type does not rely on wheelspeed to apply bias or lock!

Torsen do not wear when biasing torque although it is tempting to think that they must due to the internal friction. Friction reduces wear if of it is static friction, which it generally is inside a Torsen. Only sliding friction causes wear and there is very little of that when a Torsen is biasing torque and not very much when it is differentiating.

You seem to be saying that the Torsen is fully locked (up to bias ratio limit anyway) when biasing and fully open when differentiating.
However I think the whole idea of the "TORque SENsing" Torsen is that it acts open when no torque is applied, and applies increasing lock or bias with greater applied torque. So when you're accelerating while cornering the diff can be both differentiating and biasing. So there is sliding friction while under load. Which generates heat and causes wear. Granted this wear may be slow enough that the diff doesn't wear out within the design lifetime of the vehicle.

Anyway, that's been my understanding of it...

But, I concede it is difficult to understand how this ingenious device actually works. Thinking it gives progressive limited slip is the biggest misconception and affects how you drive these cars. You either know, or you don't.

Again, I thought progressively more lock or bias with applied torque was the whole idea...

Originally Posted by Gforce

I also point out that the space saver spare, of any size, would be completely worn out and down to the belts long before the slightest wear could have occurred inside the Torsen.

Disagree. There's gonna be heat and wear with the thing constantly differentiating while drive torque is applied while driving great distances in a straight line.

Clutch type LSD use a centrifugally activated clamping system of clutch plates, which is why electronically controlling these is preferred.

That is NOT how a clutch type limited slip works at all! See above ^^^
There will generally be some breakaway torque which gives some lock or bias right off the bat. Then you get increased clamping with increased *applied torque*. Wheelspeed has nothing to do with it!

These LSD are only wheelspeed sensitive and do not engage unless a difference in wheelspeed is experienced. They react to that. They do not limit slip until a preset wheelspeed difference is achieved. Then they lock pretty firmly and any differentiation results in wear and heat.

Good God, totally wrong!

AGain, viscous and gerotor types *are* activated by differential wheelspeed, but definitely NOT the clutch type, whether "plain" or Salisbury.

Most of the heat inside a open differential comes from the gear speed, nothing to do with limiting slip. Clutch type LSD heat up because they must allow the clutches to slip to permit differentiation. Torsen do not.

IF you run a very low breakaway torque, clutch type lsd clutches can last a VERY long time. I ran one in my 240Z with only ~23 lb-ft breakaway for probably 80k street miles and 80 or so track days and it worked great the whole time, never had to replace clutch plates.

Clutch type only react to wheelspin.

Not true.

And Torsen do not wear when they are biasing torque. On the contrary, they simply differentiate as would an open differential while transferring torque. Friction does not necessarily cause wear. Only sliding friction can cause wear and not much sliding goes on inside a Torsen when it is biasing torque.

Here's where the friction happens, guaranteed that wear is also happening there.

Again, it may last the life of the vehicle but wear and heat do occur under load when there are different output speeds.,