Found a front LSD!!

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Re: Found a front LSD!!

Postby masco » Mon Nov 19, 2012 4:51 pm

The Audi Quattro four wheel drive system has been using torsen center differentials for years. Since Quattro Gen 2 in the late 80's.

I was wondering if he would entertain the idea of having a TWIN "type 3, T-3, type c" Torsen with an uneven torque split. He could build the front and center differentials into the same unit/location [as per stock] and possibly save cost by elemininating the viscous coupler with a "spool", of sorts.
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Re: Found a front LSD!!

Postby athousandleaves » Mon Nov 19, 2012 7:00 pm

masco wrote:The Audi Quattro four wheel drive system has been using torsen center differentials for years. Since Quattro Gen 2 in the late 80's.


Quattro suffers from limited traction on 3 wheels when one wheel slips so if you get one wheel in the air on a corner you'll experience diminished power to the other three. With the viscous center you can get one wheel in the air and still have 50% torque at 2 wheels and possibly some power at the third depending on the other types of diff used.

Even though the viscous unit may introduce some understeer to the system I feel it gives a lot of benefits of a clutch type diff without all the work and can't see any really good reason to replace it with a very expensive untested helical diff.
Last edited by athousandleaves on Mon Nov 19, 2012 7:52 pm, edited 1 time in total.
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Re: Found a front LSD!!

Postby BADNEWS » Mon Nov 19, 2012 7:50 pm

athousandleaves wrote:
Even though he viscous unit may introduce some understeer to the system I feel it gives a lot of benefits of a clutch type diff without all the work and can't see any really good reason to replace it with a very expensive untested helical diff.



The only reason is because he said he can't make a front diff unless he does the center too. That is why. For Frana it's either both or none.

I agree that the VC is a good enough unit. We can even upgrade ours, which I am in the process of doing. I ideally would like to just put a helical style front diff in and leave my stock center with a upgraded VC. But right now that is not an option. I truly hope Quaife makes just a front diff and solve all our problems. But I only see it happening for a larger number of people than we can get to commit. And at a higher price than everyone is expecting. I am willing for pay as much as $2000 for just a front helical LSD that goes with the Stock center diff.
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Re: Found a front LSD!!

Postby masco » Tue Nov 20, 2012 3:13 pm

In my opinion, the main advantage of the helical differentials is the variable torque biasing characteristics. Obviously three Torsens isn't the best choice for drag racing or off-road racing or even autox. But with three helical differntials and a proper suspension set up to maintain traction, you can build a very capable car. Especailly if the center torsen is high biased, like 80-88% or so. I think most cars here are street driven and a lot of people here could benefit from a front, center and rear helical differential. The autocrossers would probably want to change to a rear clutch based LSD. The drag racers would want more locked differentials. That said, i'm highly interested in having three helical differentials in my car.
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Re: Found a front LSD!!

Postby phattyduck » Tue Nov 20, 2012 4:22 pm

Would the viscous coupler be able to remain in place with the helical center and front diffs? If that's the case, you get the best of both worlds. The question boils down to whether the transfer shaft for the front output side of the center diff remains in place. (not sure if those are the correct terms, but since the viscous coupler is separate from the center diff, it might be able to remain in use)

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Re: Found a front LSD!!

Postby underscore » Wed Nov 21, 2012 1:55 am

I thought that the VC was the center diff?

I'm not interested in anything that causes me to have to remove the rear Torsen I already have, or go to an uneven torque split. To me doing something like uneven torque would be the biggest gamble when we have nothing to reference to.
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Re: Found a front LSD!!

Postby masco » Wed Nov 21, 2012 1:46 pm

In our stock transmissions, the front and center differentials are open differentials with spider gears and are built into one unit. You cannot add just a front helical, as spider and helical differential designs are incompatible. The viscous coupler, located beside the front/center diff acts on the open center differential to provide limited slip duties. I'm assuming this new design might use the space reserved for the viscous coupler for the the center or front differentials. In other words, im not sure if this new design will still house the center and front differentials in the same unit.

The rear end is a seperate unit and you're free to do whatever you want to it.

Helical differentials are a 50/50 torque split, until slippage occurs, in which case they are able to multiply the torque applied to the slipping wheels by the torque bias ratio (TBR) of the differential and apply it to the wheels with grip. They are infinately variable and instantaneous. For instance, a helical center differential with a TBR of 4:1 will be able to deliver up to 4 times the torque of the splipping drive side to the side with grip. Since helical differentials are simply torque multipliers, they act as open differentials when there is no traction (resistive force) on one side. It would be great if we could retain the use to the viscous coupler for use in those situations, but if it was active the whole time it would reduce the torque biasing properties of the helical differential itself. There are some companies that make hybrids.

Each type of differential is has it's pros and cons so please do your homework. In anycase I hope i've cleared some stuff up.
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Re: Found a front LSD!!

Postby donk2k » Tue Nov 27, 2012 6:41 pm

masco wrote:In our stock transmissions, the front and center differentials are open differentials with spider gears and are built into one unit. You cannot add just a front helical, as spider and helical differential designs are incompatible. The viscous coupler, located beside the front/center diff acts on the open center differential to provide limited slip duties. I'm assuming this new design might use the space reserved for the viscous coupler for the the center or front differentials. In other words, im not sure if this new design will still house the center and front differentials in the same unit.

The rear end is a seperate unit and you're free to do whatever you want to it.

Helical differentials are a 50/50 torque split, until slippage occurs, in which case they are able to multiply the torque applied to the slipping wheels by the torque bias ratio (TBR) of the differential and apply it to the wheels with grip. They are infinately variable and instantaneous. For instance, a helical center differential with a TBR of 4:1 will be able to deliver up to 4 times the torque of the splipping drive side to the side with grip. Since helical differentials are simply torque multipliers, they act as open differentials when there is no traction (resistive force) on one side. It would be great if we could retain the use to the viscous coupler for use in those situations, but if it was active the whole time it would reduce the torque biasing properties of the helical differential itself. There are some companies that make hybrids.

Each type of differential is has it's pros and cons so please do your homework. In anycase I hope i've cleared some stuff up.


I can't see why we could not use it alongside the torque sensing center diff.. (In my understanding the torque sensing diff will sense torque rather than actual speed difference. So the torsen diff could do its job unaffected by the viscous coupler.)
Scenario 1:
If we get wheel spin on the front wheels the torsen will almost have been beaten in the job of securing traction. In a case like that the viscous coupler will help the torsen to limit speed difference on the axles.
Scenario 2:
The grip/torque difference available in front and rear is present but not great enough to make any wheels spin.
Then the torsen will do its job as it uses to, and the viscous coupling will do "nothing" because there is no speed difference between front and rear.

So I my opinion the torsen front center and whatever you would like in the rear + a uprated viscous coupling would be the best "traction retaining system" that you can get for a "street/auto x (all other than dragrace) -car".
It will not lock up the drive-train during parking and such.
It will last forever without servicing parts (maybe except viscous coupling, but think the uprated one will last for a long time). (If you don't brake something)

All this is my way of understanding it, and may be totally wrong.
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Re: Found a front LSD!!

Postby st185-sainz » Thu Nov 29, 2012 8:50 pm

So I my opinion the torsen front center and whatever you would like in the rear + a uprated viscous coupling would be the best "traction retaining system" that you can get for a "street/auto x (all other than dragrace) -car".
It will not lock up the drive-train during parking and such.
It will last forever without servicing parts (maybe except viscous coupling, but think the uprated one will last for a long time). (If you don't brake something)


I'm totally your opinion! If anybody will make a front torsen unit I would also like to get one after somebody tested it. I don't like being the first as I don't want to retire when I'm at a rally.

Visco Coupling will need no service under normal use. I talked to my supplier when I bought mine and he said that if I'm using my car for 5 rallies and some small events a year it will not need a revision for years!

And yes, this combination would be perfect for daily use as you do not lock up the drivetrain too much in parking and so on!
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Re: Found a front LSD!!

Postby athousandleaves » Thu Nov 29, 2012 9:21 pm

If we could get this center diff made/adapted for our transmissions then I would opt to remove the viscous for it.

http://www.youtube.com/watch?v=MjaCbpw84kw

http://www.audi.ca/ca/brand/en/exp/innovation/quattro.html wrote:Audi Quattro with Crown Gear Differential
Greater agility, outstanding traction and precisely controllable, sporty handling.
-Achieves high lock-up torque values with its multi-plate clutch packages for enhanced traction
-Distrubution of torque takes place before unwanted wheel spin can occur
-Targeted braking of inner wheels causes additional drive torque to be directed to the outer wheels, significantly improving corner traction


Of course I'd only really consider buying it if it comes with a CD of that incredibly dramatic music :P
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Re: Found a front LSD!!

Postby timmey » Sat Mar 22, 2014 10:54 pm

Interested.

I had a question: if we do a group buy of these: am I sending this guy my OEM E150 trans and I get back a trans with the LSDs installed, or am I just getting components such as the LSD, etc and additional labor to install myself? Both have their ups and downs, curious.

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Re: Found a front LSD!!

Postby tpell1221 » Thu Apr 03, 2014 2:14 am

anything happen or what
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Re: Found a front LSD!!

Postby zero06 » Thu Feb 05, 2015 5:56 am

is there something im missing here?

http://www.monkeywrenchracing.com/product_info.php?products_id=707&osCsid=gmdhqfei95neg095o0drnobbv1
is this not a quaife helical front lsd for our cars?
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Re: Found a front LSD!!

Postby underscore » Thu Feb 05, 2015 6:46 am

That LSD is for 2WD cars.
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Re: Found a front LSD!!

Postby brophats » Tue Mar 10, 2015 12:53 pm

I've been looking at one of our front/center diff assemblies and it looks like the the front differential is its own integral unit inside the whole assembly, maybe just that part can be replaced with a torsen unit which wouldn't affect the center differential. It would require a little more work to install but i wonder if that could be an option.


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