I might be crazy, but this sounds like a good idea

[Soup DeVille]

Then how come only one wheel spins in an open diff? And if the LSD sends more torque to the faster moving wheel, well, isn't that the one without traction?

Read my above post: I don't think I did a very good job with it though. basically, an open diff sends power down the path of least resistance. An LSD acts much the same most of the time, but has a clutch arrangement on it that fights that tendency if the speed differential between the wheel gets too high.

[Laconian]

Torsens fight the tendency if the torque differential is too high.

[Soup DeVille]

Torsens fight the tendency if the torque differential is too high.

As I doubt one is avaiable for his ranger, I though I'd skip getting into that. I already fear my explanation is about as clear as mud.

[S204STi]

Open diff sends the same torque to each side all the time no matter what.

LSD will send more torque to the faster spinning wheel

Locker sends all the torque to both wheels.

Wrong on 1 and 2.  Open diffs send power to the side with the least mechanical resistance.  This is why one tire spins and keeps on spinning.  LSDs tend to apply a braking force to the side that spins faster, and in turn shunting torque to the opposite side.

What's the difference between that and a regular LSD?

Most LSDs use clutches to equalize axle speeds, these use gears which move freely most of the time, but will lock up if side to side axle speeds vary enough.  In which case it will shift up to 100% of available torque to the opposite wheel.  This is the only design that I can think of that can actually bias torque.

[S204STi]

Think of a locker like a ratchet wrench In a turn, the inside wheel is driving, and the outside wheel ratchets ahead- no torque goes to it at all.

An open diff is exactly that- a differential. The sum speed of both wheels will always equal exactly twice the speed of the ring gear. On dry pavement in a straight line- that's a 50/50 split: both wheels match the speed of the ring gear. Lift one wheel off the ground and the torque follows the path of least resistance- the wheel that's on the ground is going to resist being moved, so it won't. The one in the air will spin at twice the speed of the ring gear: the sum of the speeds stay the same: one tire moving twice the ring gear speed, the other moving not at all. In a situation where one wheel is one ice or mud- where one wheel has 25 percent of the traction it will recieve 75 percernt of the torque. The wheel with 75 percent of the traction will recieve 25 percent of the torque.

A typical friction plate LSD works like an open diff most of the time: but will only let one wheel go a certain percentage faster than the other before it essentially applies the brakes on the free spinning wheel via plates in the differential gear itself. (torsen type or heical gear LSD is slightly different)

The effect when you're driving is such that on an open diff or a plate LSD, the vehicle acts as if its being pushed from the middle of the axle pretty much all the time. On a locker, it will act is as if its being pushed from the slower tire- the inside one during a turn.

QFT!

[Rupert]

I went the How Stuff Works.

I'm still kind of confused about how LSDs and lockers work, but I think I've got the open diff down. The way they explain it, in an open diff, torque is distributed equally between the wheels. They say that when traction is good, the maximum torque available is determined by the engine, but when conditions are slippery, maximum torque is determined by traction available. So, when a wheel slips, the amount of torque that is available to the non-slipping wheel is the same as the maximum torque available to the slipping wheel, as determined by the traction to that wheel. When the slipping wheel has very little traction, the non-slipping wheel gets very little torque, and the vehicle doesn't move.

LSDs, uh, transfer some of the torque from the slipping wheel to the non-slipping wheel... Or something? And lockers are exactly what they sound like.

Anyway, it sounds like a locker (even the one NACar suggests) would sacrifice too much everyday driveability for me, and that helical LSD sounds pretty good. After all, most of my driving is on pavement.

[Eye of the Tiger]

Wrong on 1 and 2.  Open diffs send power to the side with the least mechanical resistance.  This is why one tire spins and keeps on spinning.  LSDs tend to apply a braking force to the side that spins faster, and in turn shunting torque to the opposite side.

Most LSDs use clutches to equalize axle speeds, these use gears which move freely most of the time, but will lock up if side to side axle speeds vary enough.  In which case it will shift up to 100% of available torque to the opposite wheel.  This is the only design that I can think of that can actually bias torque.

Ok, let's say you have an open diff, one wheel is spinning, the other is not. If you lifted up the stationary wheel, would it start spinning or not?

[Rupert]

As I doubt one is avaiable for his ranger, I though I'd skip getting into that. I already fear my explanation is about as clear as mud.

A Torsen also wouldn't be any good if a wheel was in the air.

Er, but what would a normal LSD do in that situation, or a helical LSD?

Man, this shit is hard! 

[Rupert]

Ok, let's say you have an open diff, one wheel is spinning, the other is not. If you lifted up the stationary wheel, would it start spinning or not?

Yes?

You mean if one wheel was in the air and spinning, and then you lifted the other wheel, causing both to be in the air? In that case, I think both wheels would spin.

[Eye of the Tiger]

Yes?

You mean if one wheel was in the air and spinning, and then you lifted the other wheel, causing both to be in the air? In that case, I think both wheels would spin.

Right, but if all the torque applied to the wheel is suppsedly equivalent to the actual speed of the wheel, then the torque on the stationary wheel would be zero, and therefore it could not start spinning once lifted off the ground. We know this is false, because we know the wheel will, in fact, start spinning once lifted. This is because there is torque applied to the stationary wheel, and this torque happens to be equal to the torque on the spinning wheel - a 50/50 split of torque (not speed, but force of torque). The spinning wheel, once traction is broken, has low kinetic friction, which limits the amount of torque that can be applied through the entire drivetrain, and therefore limits the amount of torque that can be applied to the wheel with traction - so your car is stuck. Is this making any sense? I'm making all of this up, but I swear it's right.

[hotrodalex]

Ok, let's say you have an open diff, one wheel is spinning, the other is not. If you lifted up the stationary wheel, would it start spinning or not?

Yes, it would start spinning.

[hotrodalex]

Right, but if all the torque applied to the wheel is suppsedly equivalent to the actual speed of the wheel, then the torque on the stationary wheel would be zero, and therefore it could not start spinning once lifted off the ground. We know this is false, because we know the wheel will, in fact, start spinning once lifted. This is because there is torque applied to the stationary wheel, and this torque happens to be equal to the torque on the spinning wheel - a 50/50 split of torque (not speed, but force of torque). The spinning wheel, once traction is broken, has low kinetic friction, which limits the amount of torque that can be applied through the entire drivetrain, and therefore limits the amount of torque that can be applied to the wheel with traction - so your car is stuck. Is this making any sense? I'm making all of this up, but I swear it's right.

Torque isn't stuck to one side. It can shift. If you get rid of the force acting against the other wheel, the torque will even out again. It might take awhile for the wheels to even out their speed, but they will.

[Eye of the Tiger]

Torque isn't stuck to one side. It can shift. If you get rid of the force acting against the other wheel, the torque will even out again. It might take awhile for the wheels to even out their speed, but they will.

You're mixing up torque and wheel speed. Torque is a force, not a motion.

[hotrodalex]

You're mixing up torque and wheel speed. Torque is a force, not a motion.

Well apparently if the wheel is moving, it's getting torque.

[Eye of the Tiger]

Well apparently if the wheel is moving, it's getting torque.

The non-moving wheel has the same amount of torque - it's just not enough to move it, because it has too much traction and/or it's not enough torque to move the car.

[Soup DeVille]

A Torsen also wouldn't be any good if a wheel was in the air.

Er, but what would a normal LSD do in that situation, or a helical LSD?

Man, this shit is hard! 

Yeah, a torsen or helical both require some resistance on both wheel to develop a torque bias between the wheels, so if one wheel was in the air it wouldn't work.

A "normal" clutch type LSD relies on the speed difference between the two, so it would.

[Eye of the Tiger]

Yeah, a torsen or helical both require some resistance on both wheel to develop a torque bias between the wheels, so if one wheel was in the air it wouldn't work.

A "normal" clutch type LSD relies on the speed difference between the two, so it would.

The only real solution here is a Lincoln Locker. 

[Soup DeVille]

The only real solution here is a Lincoln Locker. 

Its actually not as bad as you would think.

[Eye of the Tiger]

Its actually not as bad as you would think.

Just wears the tires a bit. 

[Soup DeVille]

Just wears the tires a bit. 

The road is my differential!

[S204STi]

Ok, let's say you have an open diff, one wheel is spinning, the other is not. If you lifted up the stationary wheel, would it start spinning or not?

Not necessarily.

Let's say you lift the rear axle entirely off the ground.  Only one wheel will spin, usually.  I am not sure that I can explain why, except to say that because the side gears in the gearset aren't mechanically joined there is allowance for a difference in speed, and at a certain point one will overrun the other and all of the available torque will go to that side.

[S204STi]

Yeah, a torsen or helical both require some resistance on both wheel to develop a torque bias between the wheels, so if one wheel was in the air it wouldn't work.

A "normal" clutch type LSD relies on the speed difference between the two, so it would.

Did not know that!

[Soup DeVille]

Did not know that!

Or so I've been told...

[S204STi]

FWIW traction control systems that apply brake force to the wheels act in much the same way.  By braking the spinning wheel it is applying torque to the one that isn't.  People bash these systems, yet in some ways they are capable of so much more than normal mechanical means.

[Eye of the Tiger]

Not necessarily.

Let's say you lift the rear axle entirely off the ground.  Only one wheel will spin, usually.  I am not sure that I can explain why, except to say that because the side gears in the gearset aren't mechanically joined there is allowance for a difference in speed, and at a certain point one will overrun the other and all of the available torque will go to that side.

I don't know what you mean. ALl I know is, if the whole axles is in the air and one wheel starts spinning, it takes only a minimal amount of torque to do so, and that same amount of torque applied to the other side might not make that wheel spin for whatever reason, perhaps brake drag... The point is, wheel speed and torque are independant of each other, and a spinning wheel can have the same torque applied to it as a non-spinning wheel. Open diffs are 50/50 split with torque.

[S204STi]

Or so I've been told...

I'm with you, this shit is really confusing so I'm just going with what I've been told.

[S204STi]

I don't know what you mean. ALl I know is, if the whole axles is in the air and one wheel starts spinning, it takes only a minimal amount of torque to do so, and that same amount of torque applied to the other side might not make that wheel spin for whatever reason, perhaps brake drag... The point is, wheel speed and torque are independant of each other, and a spinning wheel can have the same torque applied to it as a non-spinning wheel. Open diffs are 50/50.

I understand that, but torque has its outlet in wheel speed.  Torque wants to go somewhere.

[hotrodalex]

I'm with you, this shit is really confusing so I'm just going with what I've been told.

I just buy one of each type of differential and see which one is the least suck-ish.

[S204STi]

I just buy one of each type of differential and see which one is the least suck-ish.

lawl

[Eye of the Tiger]

I understand that, but torque has its outlet in wheel speed.  Torque wants to go somewhere.

The outlet of torque is power, but torque is still there whether or not there is power. The torque is applied to both sides equally, but the total amount of torque is limited when a wheel loses traction, and a spinning wheel against the ground has very low traction due to kinetic friction. The same small amount of torque that keeps that spinning wheel spinning, is the same amount of torque being applied to the other wheel. If a traction control system applies brakes to the spinning wheel, then the torque required to spin that wheel increases, and since torque is always equal on both sides of an open diff, the other wheel shares in the increase of torque, allowing it to push the car.