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Electronic Differential Lock Test with Open Diff

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Old Jan 21, 2015 | 01:59 PM
  #11  
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Originally Posted by 11screw50
If it is using the ABS, it is an electronic limited slip.

If it were an electronic locker, you would have driven right off that jackstand.

Once a wheel is off the ground, limited slip is of limited use.
Yes, of course it's electronic limited slip.
And one wheel was completely off the ground, and it was very useful and controllable.
That was my test.

Did you not read my entire post?
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Old Jan 21, 2015 | 02:01 PM
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Originally Posted by MEZERR
The one tire was probably jacked up 1", on the axle housing. If he drove forward too far, the jack stand would just tip forward, and he'd be back on all 4 wheels. He was in the truck, applying light throttle. I don't see this as dangerous, or risky.
Exactly!
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Old Jan 21, 2015 | 03:33 PM
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Originally Posted by MEZERR

The one tire was probably jacked up 1", on the axle housing. If he drove forward too far, the jack stand would just tip forward, and he'd be back on all 4 wheels. He was in the truck, applying light throttle. I don't see this as dangerous, or risky.
Never said dangerous or risky. I'm thinking..stupid would be a better word.

Your truck, your driveway. Have at it!
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Old Jan 21, 2015 | 03:47 PM
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Originally Posted by kobayashi maru
Question(s): Why is a LSD ineffective when one wheel is off the ground? Is it because the torque bias overwhelms the coupling? Are some LSDs better than others in this regard?
Because the Elocker does not have a true LSD, it is more of a simulated one.
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Old Jan 21, 2015 | 04:05 PM
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Originally Posted by BucketMan
Never said dangerous or risky. I'm thinking..stupid would be a better word.

Your truck, your driveway. Have at it!
Alright, I'll bite. Why would it be stupid?
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Old Jan 21, 2015 | 04:16 PM
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Originally Posted by vozaday
Because the Elocker does not have a true LSD, it is more of a simulated one.
I'm aware of that but I'm curious on a mechanical level whether it's a true LSD or simulated. Both are designed to deliver more torque to the slower wheel so one would logically think that having a wheel off the ground is a pure example of this, if a little extreme.
So I have to imagine that the reason it fails in this scenario is because the torque transfer is not efficient enough hence the need for a locking diff?

Sorry for the thread-jack but I only have rudimentary knowledge of how LSDs work so I want to find out if my understanding of the testing results is correct.
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Old Jan 21, 2015 | 04:29 PM
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Originally Posted by kobayashi maru
I'm aware of that but I'm curious on a mechanical level whether it's a true LSD or simulated. Both are designed to deliver more torque to the slower wheel so one would logically think that having a wheel off the ground is a pure example of this, if a little extreme.
So I have to imagine that the reason it fails in this scenario is because the torque transfer is not efficient enough hence the need for a locking diff?

Sorry for the thread-jack but I only have rudimentary knowledge of how LSDs work so I want to find out if my understanding of the testing results is correct.
Hope this answers you question some.

The Simulated works off an Open Diff, which you said you knew. This works by pulsing the brakes on the faster side. Since it is an open diff, while the brakes are engaged on the faster wheel, the slower wheel gets most of the torque, hence the reason he said it would make small jumps, and got more traction as he went faster. If he would have revved higher it probably would have fallen off the jack stand. But the system does have it's limits, as do all systems.

The mechanical LSD, either works off clutch packs or a Torsen(Spell check) system. The Torsen system uses a series of gears to transfer torque, and the clutch pack, well uses a big spring to put pressure on the axles to force torque transfer over. And with Both clutch and torsen the faster wheel, if off the ground will free spin, unless the brakes are pumped to transfer torque faster.

The video below demonstrates the brake pump, which even on an open diff is useful, but a LSD, makes it transfer faster and for longer duration, when couple with the pump. That's why I pointed out the 1 Wheel spin control on the trucks coupled with a LSD, would be pretty bad ***, it pumps the brakes faster then we ever could.

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Old Jan 21, 2015 | 04:33 PM
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Originally Posted by kobayashi maru
So I have to imagine that the reason it fails in this scenario is because the torque transfer is not efficient enough hence the need for a locking diff?
^ this. Im willing to bet that if he gave it some gas, if would brake the airborne wheel and send power to the grounded wheel and propel the truck forward off the jackstand.
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Old Jan 21, 2015 | 05:15 PM
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Thanks RajunKajun! That was the explanation I was looking for. So I guess I was fundamentally correct in my thinking but had some gaps in knowledge which you nicely filled in

One thing I failed to realize earlier is that the simulated LSD utilizes the ABS system to pump the brakes rather than simply apply them linearly. I see the limitation more clearly now. YouTube is blocked at work so I'll check that out later but I see what you're saying about combining brake control + true LSD.
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Old Jan 21, 2015 | 05:19 PM
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Originally Posted by Kytann

Alright, I'll bite. Why would it be stupid?
Planted wheel grabs, truck goes forward, Murphy's law takes over and the jack stand grabs a brake line ABS line, etc..

Would suck to break some stuff over a question that could be easily answered here or on YouTube as others have shown.
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