If I am understanding the lsd right

[b*saint]

As the spider gears try to come out of their grooves (ramps) from the torque of the engine spinning, they compressed the clutch plates stack (similar to a motorcycle wet clutch) which are groved to the housing of the lsd which is in turn bolted to the rack locking everything up. If Im am correct what does the % lockup mean? How much torque it takes to overcome the clutch?

And anyone know what the clutch friction disks are made of? Same stuff on a bike?

[whiltebeitel]

http://auto.howstuffworks.com/differential4.htm

Same stuff in bike clutches as in clutch-type lsd's, generally speaking. The friction material can be organic to metallic substances, depending on application.

[b*saint]

Thats not our lsd though in that link and they really are giving general information.

[SpecM]

I like to know also, what does the "% lockup" refer to?

[Jean]

The % of power difference lsd can shift between left and right sides.

[b*saint]

From looking how it goes together I don't understand how it can shift power. Maybe thats why there is 4 spider gears? Explain to me the mechanics of how it shifts power.

[whiltebeitel]

Thats not our lsd though in that link and they really are giving general information.

There is no special voodoo to the BMW differentials, they are very simialr to the "Eaton" style diff. They use Bellville springs (slightly conical washers) stacked in a specific pattern to apply a force to the clutches. The principles are the same. The clutches will hold up to specific torque (dependent on the stacking of the Bellville springs). The spider gears allow the wheels to spin at different speeds (this must happen when turning, or the tires will lose traction, thus the "hopping" of welded differentials).

The clutches will resist this change in speed to a degree. When their ability to resist the difference between the wheels, they allow one wheel to spin to a lesser degree than the open diff, and the non-slipping wheel is given a portion of the torque applied by the engine (the breakaway torque, to be specific). The rest goes to the slipping wheel.

If that "HowStuffWorks" article (read all the pages) and this explination doesn't work, I don't know what will.

[b*saint]

No thats not what I am looking for. According to the bmw manual, the more input torque applied to the differential that harder it locks. How? Thats the info I am looking for. I get the springs and spider gears and all that crap. The BMW lsd is the only lsd Ive seen in my hands. I dont know how detroit or quaife or what nots work.

[Aptyp]

it has little friction disks (aka clutches) they look like sand paper disks. What happens is that wheels spins at the same speed, but when one side loads, at 25% power is distributed to the loaded wheel, because those friction disks slip. And that's how magical BMW diff works.

You can make diff. 50% diff by adding an extra friction disk, or even make it a 75% by shaving one of the plates and adding 3 disks. Or you can make it 100% by welding your open diff.

[BigD]

No thats not what I am looking for. According to the bmw manual, the more input torque applied to the differential that harder it locks. How? Thats the info I am looking for. I get the springs and spider gears and all that crap. The BMW lsd is the only lsd Ive seen in my hands. I dont know how detroit or quaife or what nots work.

That's a torsen diff (quaife is the same thing). It's 100% open without load (or if you lift a wheel) and 100% locked under load. Clutch packs and viscous have a constant slip ratio. I don't know of any BMWs with torsens, but sounds like you are reading the manual from one. The E30 has a clutch pack.

[b*saint]

I guess the BMW manual could be describing a diff they dont use.

[Wh33lhop]

That's a torsen diff (quaife is the same thing). It's 100% open without load (or if you lift a wheel) and 100% locked under load. Clutch packs and viscous have a constant slip ratio. I don't know of any BMWs with torsens, but sounds like you are reading the manual from one. The E30 has a clutch pack.

Torsens don't lock up in the same sense that a viscous or clutch type LSD do (which would be, apply more torque to the slower spinning wheel and less to the faster spinning wheel). They provide more torque to whichever wheel gives more resistance, no matter either wheel's speed. Torsens also don't work when one wheel is off the ground because of this.

This is also why torsens are good for FWD applications, because they apply more torque to the outside wheel in a corner, effectively rotating the car better (the outside wheel is spinning faster, so a clutch type or viscous would actually apply more torque to the inside wheel before wheel slip occurs). Same goes for center diffs, torsens work well since they don't have a "locking" action they don't make the front and rear wheels fight against each other in a corner when power is applied.

As for the original question, the more torque is applied to the diff overall, the harder the clutch packs are squeezed (due to the ramps effectively pressing on them harder), which creates more friction and attempts to match each axle speed to the entire assembly speed, much like a clutch is squeezed in between a flywheel and pressure plate, which attempts to match the engine speed and input shaft speed.

[Hellabad]

There is no special voodoo to the BMW differentials, they are very simialr to the "Eaton" style diff. They use Bellville springs (slightly conical washers) stacked in a specific pattern to apply a force to the clutches. The principles are the same. The clutches will hold up to specific torque (dependent on the stacking of the Bellville springs). The spider gears allow the wheels to spin at different speeds (this must happen when turning, or the tires will lose traction, thus the "hopping" of welded differentials).

The clutches will resist this change in speed to a degree. When their ability to resist the difference between the wheels, they allow one wheel to spin to a lesser degree than the open diff, and the non-slipping wheel is given a portion of the torque applied by the engine (the breakaway torque, to be specific). The rest goes to the slipping wheel.

If that "HowStuffWorks" article (read all the pages) and this explination doesn't work, I don't know what will.

Dude thats totally wrong. I will post in the thread later with the real info.

Jay Morris from Ground Control

[b*saint]

Torsens don't lock up in the same sense that a viscous or clutch type LSD do (which would be, apply more torque to the slower spinning wheel and less to the faster spinning wheel). They provide more torque to whichever wheel gives more resistance, no matter either wheel's speed. Torsens also don't work when one wheel is off the ground because of this.

This is also why torsens are good for FWD applications, because they apply more torque to the outside wheel in a corner, effectively rotating the car better (the outside wheel is spinning faster, so a clutch type or viscous would actually apply more torque to the inside wheel before wheel slip occurs). Same goes for center diffs, torsens work well since they don't have a "locking" action they don't make the front and rear wheels fight against each other in a corner when power is applied.

As for the original question, the more torque is applied to the diff overall, the harder the clutch packs are squeezed (due to the ramps effectively pressing on them harder), which creates more friction and attempts to match each axle speed to the entire assembly speed, much like a clutch is squeezed in between a flywheel and pressure plate, which attempts to match the engine speed and input shaft speed.

Ramps are the "V" that the spider gear shafts sit in right?

[Wh33lhop]

Ramps are the "V" that the spider gear shafts sit in right?

Yes.