Stock vs aftermarket lsd

[dmad_dood]

Hi there everyone,

Im looking at changing the diff on my na8. How do the mazda torsen's compare with aftermarket lsd's like cusco, kaaz, tomei etc

Also wheres the best place to buy an lsd either aftermarket or stock. Don't mind in Australia or out as long as its quick shipping.

Cheers.

[hks_kansei]

Torsens are a Torsen LSD centre.

Kaaz, Cusco, etc are normally clutch pack LSDs.


Each diff has different characteristics from behind the wheel, and each is suited to slightly different scenarios.

For example, on a road dríven MX5 I'd not hesitate to put in a Torsen. Long life, no need for fancy LSD oils, quiet and easy to live with.
If I wanted to drift though, I'd get a clutch pack diff, more predictable when sliding, but chattery at low speeds and wears faster than a torsen (clutches need replacing after a while)

A torsen uses helical gears etc to bias the drive torque to the wheel with more grip (to a certain point)
A clutch pack locks both wheels together as though it's a solid axle (while it's locked, which depends on 1/1.5/2 way, and the internal settings as to how hard to lock)

[dmad_dood]

Torsens are a Torsen LSD centre.

Kaaz, Cusco, etc are normally clutch pack LSDs.


Each diff has different characteristics from behind the wheel, and each is suited to slightly different scenarios.

For example, on a road dríven MX5 I'd not hesitate to put in a Torsen. Long life, no need for fancy LSD oils, quiet and easy to live with.
If I wanted to drift though, I'd get a clutch pack diff, more predictable when sliding, but chattery at low speeds and wears faster than a torsen (clutches need replacing after a while)

A torsen uses helical gears etc to bias the drive torque to the wheel with more grip (to a certain point)
A clutch pack locks both wheels together as though it's a solid axle (while it's locked, which depends on 1/1.5/2 way, and the internal settings as to how hard to lock)

Cool, so whats the difference between the torsen 1 and torsen 2. Ive been doing some reading and apparently the torsen 1 is biased to acceleration where the 2 is biased to decel (although from what ive heard theres no real noticeable difference between the two types).

And now.. i've heard several times that torsen's virtually don't wear out due to the lack of clutches and what not. Must i be scared buying second hand??

Also what gearing is the stock na8 open diff?

Thanks,

Jono

[hks_kansei]

Cool, so whats the difference between the torsen 1 and torsen 2. Ive been doing some reading and apparently the torsen 1 is biased to acceleration where the 2 is biased to decel (although from what ive heard theres no real noticeable difference between the two types).

And now.. i've heard several times that torsen's virtually don't wear out due to the lack of clutches and what not. Must i be scared buying second hand??

Also what gearing is the stock na8 open diff?

Thanks,

Jono

T1 and T2 function exactly the same, the T1 has a mildly different bias ratio, but it;s like 3.2 to 3.3 or somethign like that.
T1 uses worm gears and spur gears, T2 uses helical gears. The T2 is the stronger diff, so get that if you can find one.

Torsens don't wear any more/less than an open diff, about all that wears is the belleville washers inside that help add preload. The diff still works perfectly fine without preload on them. I'd have no issues with a secondhand one. (I can give you details of a guy I know who sells fully rebuilt ones if you prefer, new bearings/washers/seals etc. He built my diff, and it's been great)

Stock NA8 is 4.1 ratio diff if I remember correctly (either that or 4.3 maybe)

[sailaholic]

Read right to the end
http://www.miata.net/garage/diffguide/

Stock na8 ratio for an Aus delivered car is 4.1, jap was 4.3.

Note that the SE diff is neither a T1 or a T2 but a third design.


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[dmad_dood]

Cool, so whats the difference between the torsen 1 and torsen 2. Ive been doing some reading and apparently the torsen 1 is biased to acceleration where the 2 is biased to decel (although from what ive heard theres no real noticeable difference between the two types).

And now.. i've heard several times that torsen's virtually don't wear out due to the lack of clutches and what not. Must i be scared buying second hand??

Also what gearing is the stock na8 open diff?

Thanks,

Jono

T1 and T2 function exactly the same, the T1 has a mildly different bias ratio, but it;s like 3.2 to 3.3 or somethign like that.
T1 uses worm gears and spur gears, T2 uses helical gears. The T2 is the stronger diff, so get that if you can find one.

Torsens don't wear any more/less than an open diff, about all that wears is the belleville washers inside that help add preload. The diff still works perfectly fine without preload on them. I'd have no issues with a secondhand one. (I can give you details of a guy I know who sells fully rebuilt ones if you prefer, new bearings/washers/seals etc. He built my diff, and it's been great)

Stock NA8 is 4.1 ratio diff if I remember correctly (either that or 4.3 maybe)

That would be great if i could get those details

Also thanks for the help.

Jono.

[kazama]

from my understanding the T1 and T2 are different in how they operate. the T1 being the more sought after and more expensive to produce diff

miata.net has a few threads on it

http://forum.miata.net/vb/showthread.php?t=44836
^one of many

[hks_kansei]

from my understanding the T1 and T2 are different in how they operate. the T1 being the more sought after and more expensive to produce diff

But also the weaker diff.

The basket case that holds the gears is a more open design, and the worm gear/spur combo are held in by a couple of split pins.

T2 has an almost fully enclosed basket, and the gears are held by the whole casing.

T1 supposedly has a slightly better bias action though.

[hks_kansei]

Note that the SE diff is neither a T1 or a T2 but a third design.

I was pretty sure the SE used a T2, just with thicker driveshafts and more splines.
The diff centre was just a T2 IIRC.

esp since T1 and T2 are about all that was available at the time, the T3 was only for central diffs on 4x4 cars from memory.

It may be a T2 Racemaster, which is just a T2 with more preload to allow the bias action when a wheel is fully unloaded.


Unless they used a clutchpack?

[sailaholic]

Quoted from the diff spotters guide.

"TOCHIGI FUJI SUPER LSD

For ’03 NB and subsequent, into the NC models the limited slip differential was changed to a Tochigi Fuji Super LSD (What appears to be an adjective, “Super”, is part of the brand name).

Well, when is a clutch not a clutch? The Torsen has clutches too, but since they are not obvious and not serviceable, and do not wear out for a long long time, they are ignored. Torsen clutches don't look like clutches either, but rather metal washers. In some cases, even the washer is omitted and the "clutching action" is a rotating gear against a stationary housing.

The Tochigi Fuji Super (TFS) uses cone clutches made of metal which I assume is machined to exacting tolerance and hardened. Cone clutches can transmit higher torques for a given diameter than traditional flat plate clutches.

Flat plate clutches can increase their capacity by adding plates and selection of materials that have higher friction. Traditional LSD use both of these and it is the wear of the friction material, and reduction of preload, that demands periodic rebuild.

Once we figure out which clutch to use, there is the matter of how to actuate the clutch. Typically a spring provides preload so there is some friction to drive the clutches. From there a ramp, cam, or gear forces provide the muscle to clamp the clutch closed so it can transmit torque from one axle to the other. Often the speed difference between the axles is key to generating this clamping force. This is the reason these LSD are called "speed sensing".

The Kaaz uses a ramp. While our TFS uses the force provided by the driving spider gears to spread the side gears. The side gears slide on the splined axle shafts and spread apart. This spreading is constrained by the cone clutches pushing against the differential case (by differential case, I don't mean the housing you see under the car, but the working part of the unit mounted in and spinning with the ring gear).

Torsen TBR is about 2.5 to one, decreasing slightly from Type I to Type II Torsen. The TFS has slightly less capability to move torque from one wheel to the other with a TBR of 2.0. To the extent that the TBR is reduced, the LSD becomes less interesting to the competitive driver. Race car guys use an RX7 clutch unit, Kaaz, or a spool. For sporting street use the TBR in the realm of 2.0 to 2.5 is certainly an improvement, while being very unobtrusive. How many people post here that they can't tell if they have a Torsen or not?

So, do the TFS clutch cones wear out? Apparently Mazda doesn't think so for a long time since they are not serviceable.

Is the TFS "torque sensing"? Well, sort of. Remember the marketing strength of "synthetic" oil, so companies jumped on board with "synthetics" that weren't synthetic? This is the same think. Differential manufacturers have been looking at the real Torsen with their "torque sensing" marketing and have been wanting a piece of that. Many types of clutch LSD use the torque coming through the driveshaft to lock the clutch pack tighter. The TFS? THe harder you drive it (torque) the harder it locks, so you can call it torque sensing if you like.

The TFS and Torsen do share one characteristic and that is they do not wear (like traditional clutch pack units) during low torque differentiation (coasting in a turn or driving with mismatched tire sizes). A Kaaz will fry the clutch packs because it is a "speed unit" and it doesn't care or know what torque it is transmitting.

To me, a "torque sensing" differential has helical gears, not cone clutches. But, I'd hate to defend that position in court"


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[dmad_dood]

Will a torsen 1.8 centre fit into a 1.8 open housing? Also whats involved in fitting a centre into a housing do i need to worry about setting preloads as its a torsen or anything like that?

[Locutus]

Yes, with the exception of the SE diff. The SE diff requires the SE carrier and shafts.

[sailaholic]

Setting preloads is all done at the factory as the centre is complete. Not sure if you need to set back lash for the crown wheel and pinion though?


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[hks_kansei]

Setting preloads is all done at the factory as the centre is complete. Not sure if you need to set back lash for the crown wheel and pinion though?


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You certainly do, if it;s wrong they can chew each other apart.


Also, Torsen is a trademark name, it stands for Torque Sensing, but doesn't refer to all "torque sensing" diffs.
Same as KFC stands for Kentucky Fried CHicken, but that doesn't mean that any chicken fried in Kentucky is "KFC"

http://en.wikipedia.org/wiki/Torsen

[flycasta]

The SE torsen is a T2 type as well. It however doesn't have the small bellville washers inside it like the N/A T2 that preload the side gears. The pricinple is exactly the same in both with the only difference being the Biasing. I have never sat down to work out the biasing ratios but the helical gears and side gears inside each are almost identical with the way they look and fit inside the cases. As I said small parts inside them are different with the SE having just 2 thrust washers in between each side gear where the N/A T2 has a spring washer setup to help preload the side gears by pushing them apart. I generally replace a little thrust washer inside them, at the end of the spring washer stack, and also add a very thin extra spring washer to add a little more preload too make them a little tighter.

Will a torsen 1.8 centre fit into a 1.8 open housing? Also whats involved in fitting a centre into a housing do i need to worry about setting preloads as its a torsen or anything like that?

Yes it will but if you want a diff shop to remove your diff, strip it, Fit the Torsen and refit the complete diff you could be looking at anywhere from $500 up to $800 Including new bearings etc if they want to do that at the same time as insurance for themselves. You will need to reset the backlash if doing it yourself but the Torsen itself will bolt straight up just like the open centre.