Torsen vs standard Traction lok LSD differential pros and cons?

[TeeLew]

I think the Detroit tru-trak has clutches. It will drive with one wheel in the air unlike the torsen.

Judging by the exploded view on their site, I don't think they do. That might be a simplified view, though.

If it is able to drive with one wheel in the air, it's due to preload. I ran a Quaife (a different manufacturer with a similar approach) a long time ago that had a small stack of belleville washers which provided the ability to change preload. This would provide some amount of drive with 1 wheel in the air.

Generally speaking, if you've got a rear tire in the air for any significant portion of time on a rear wheel drive car, you've got bigger problems than just the diff.

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[shogun32]

Worm gears work great on the 'drive' side, but they're inefficient when being driven by a spur gear.

a turning worm gears drives the gear it's meshed with but the meshed gear can not drive the worm. It locks up solid. Or the worm helical angle is so incredibly shallow the edge of the straight gear is able to turn the worm. Would make for NASTLY level of wear unless the edge of the teeth were cut to match the helix.

Ok, I see my problem. Either I'm a moron or I swear I've seen illustrations where the worm wheel is driving straight gears, not a worm gear. So that under wheel slip the straight gear (not the spurs) on the axle tries to drive the worm, can't and so forcibly spins the whole worm+spur assembly around the axis thus fully locking both sides and converting it to a solid axle.

 

[Brian@BMVK]

thus fully locking both sides and converting it to a solid axle.

Negative.

 

[Norm Peterson]

Less. About 5-10% less TBR. Going up to the 75W140 from 75W90 has about a 10% reduction in TBR also.

Thanks, Brian. That's about what I was thinking.


Norm

 

[Brazos609]

I think the Detroit tru-trak has clutches. It will drive with one wheel in the air unlike the torsen.

No, the Detroit Truetrac does not have clutches, it is a gear driven limited slip differential.

 

[Vlad Soare]

In the end is there such a thing as a perfect TBR? My guess is no, there isn't. Because when a wheel loses traction you want the TBR to be as high as possible, but round a corner with good traction on both wheels you want it to be as low as possible. I guess you can only increase the TBR so much before you become unable to drive round corners without wheel slip, right?
In an ideal world if a wheel, due to lack of grip, were only able to put down x% of the input torque, then the other wheel would instantly receive (100 - x)%. But I guess that's not possible, is it?

 

[ice445]

In the end is there such a thing as a perfect TBR? My guess is no, there isn't. Because when a wheel loses traction you want the TBR to be as high as possible, but round a corner with good traction on both wheels you want it to be as low as possible. I guess you can only increase the TBR so much before you become unable to drive round corners without wheel slip, right?
In an ideal world if a wheel, due to lack of grip, were only able to put down x% of the input torque, then the other wheel would instantly receive (100 - x)%. But I guess that's not possible, is it?

Everything is a compromise. TBR is a tool to get the desired result, which is different for every car, driver, and track or usage setting.

 

[Vlad Soare]

Yeah, but what if the desired result is: "allow the wheels to rotate at different speeds as long as both have grip, but lock them together tightly as soon as one of them slips". Is there a diff that can achieve this? I take it the Torsen can't.
And even if this were possible, would it be a good idea? Or would it do more harm than good?

 

[Brian@BMVK]

Yeah, but what if the desired result is: "allow the wheels to rotate at different speeds as long as both have grip, but lock them together tightly as soon as one of them slips". Is there a diff that can achieve this? I take it the Torsen can't.
And even if this were possible, would it be a good idea? Or would it do more harm than good?

A truly locked diff (spool) isn't ideal for cornering, as it results in scrub due to the different speed needs for inside vs outside wheels. What you want is a diff that biases torque while maintaining near the ideal inside vs outside speed relationship in accordance with the corner radius. The Torsen does this quite well. The term "locked" is often misinterpreted when it comes to limited slip diffs.

 

[shogun32]

given this illustration I don't see how changing viscosity of oil changes anything, let alone bias in a Torsen.

 

[Brian@BMVK]

given this illustration I don't see how changing viscosity of oil changes anything, let alone bias in a Torsen.

Link on the prior page (from Torsen) describes how the change in friction changes the TBR. The viscosity and/or friction modifiers in the oil changes the internal friction.

 

[shogun32]

Link on the prior page (from Torsen) describes how the change in friction changes the TBR. The viscosity and/or friction modifiers in the oil changes the internal friction.

So what explains the RADICAL difference between the Torsen illustration and the YT and KMP illustrations claiming to describe the same thing? The Torsen graphic has the worm gear+wheel on a parallel axis. The YT illustration has them at 90deg and that is why I previously asserted there is no friction component and why the assembly immediately locks and transforms into a solid axle when one wheel slips.

I guess Torsen changed their design some time ago to introduce a TBR component when previously there was none?

 

[Brian@BMVK]

So what explains the RADICAL difference between the Torsen illustration and the YT and KMP illustrations claiming to describe the same thing? The Torsen graphic has the worm gear+wheel on a parallel axis. The YT illustration has them at 90deg and that is why I previously asserted there is no friction component and why the assembly immediately locks and transforms into a solid axle when one wheel slips.

I guess Torsen changed their design some time ago to introduce a TBR component when previously there was none?

That video has some significant inaccuracies as pointed out by commenters to the video.

 

[Elp_jc]

Does anybody have an illustration of exactly what our Ford Torsens look like? How many sets of worm gears it has: 3 or 4? It's not easy to visualize how a different fluid (or friction modifier) can alter TBR, but it does, because when you have excessive chatter, and you add FM, it stops, meaning it makes the differential less aggressive indeed.

 

[Vlad Soare]

A truly locked diff (spool) isn't ideal for cornering, as it results in scrub due to the different speed needs for inside vs outside wheels. What you want is a diff that biases torque while maintaining near the ideal inside vs outside speed relationship in accordance with the corner radius. The Torsen does this quite well. The term "locked" is often misinterpreted when it comes to limited slip diffs.

A spool is no good for cornering, but great when one wheel has no grip. A Torsen is good for cornering, but no good when one wheel has no grip at all.
What I want is a combination of both. One that's ideal in both situations. One that allows you to drive round a corner smoothly, but never, under any circumstances, spins one wheel while the other is completely stationary. If one wheel spins while the other is stationary, then I want the other to receive as much torque as is necessary for it to move.
In other words, I want the diff to allow the wheels to rotate at different speeds, but only as long as both are rotating at least to some degree. The wheels should rotate either together (at different speeds if need be), or not at all.
Is this possible? I guess not. At least not by mechanical means. Not without some kind of electronic control, based on input from the ABS sensors, or something like that.

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