helical-type limited-slip

Does anyone know if the 04 STi's helical-type limited-slip front differential will fit in our legacy's without major work? I've tried searching the material on this site, but without luck.

I thought only the '05's had the helical? But somehow, I doubt it would fit, because I believe the diff is bigger physically...

put in a Cusco LSD instead Talk to Myles at http://www.racecompengineering.com

i called over there, he's at SEMA

The front LSDs are different from the 5-speed to the 6-speed. I don't know if you could make one designed for the 6-speed fit into a 5-speed, but I doubt it. I do know that any aftermarket LSD will come in different versions for the 5 or 6 speed.

Just got off the phone with racecompengineering.com. Let me just say, super cool people, I will definitely order this unit through them in December. The Cusco front LSD is a 1.5 / 2 way hybrid, made just for the legacy, so I’m told and can be delivered in 4 to 6 weeks after order is put through.

yea, cuz I am the one who talked to you haha. No, I dont work for them, but I am there a lot to do R&D and figure out certain things with them. I was at racecomp doing some research myself.. I wasnt sure if you just wanted something that for acceleration-only type of LSD. The one that Cusco offers is a 1.5 way out of the box, but there are instructions that tell you how to make it a 2-way. If you need to know the difference, here's an easy explanation of the differences of each:

 

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

 

Here is the Cusco page that tells you how the 1-way, 1.5-way and 2-way differ:

http://www.cusco.co.jp/04ctl/04_ct.html

http://www.cusco.co.jp/05_ctg/5lsd_pdf/lsd_112.pdf

ha, i knew that voice sounded familiar, but didn't want to assume it was the great one

What is the service interval for the Cusco LSD in Legacy front diff application? I remember the rear app for the 240 is about 40K miles. Of course that's due to heavy abuse from drifting, but I wonder how harsh it is on the clutch pack for just regular driving.

 

The helical unit, although not a true locking diff, doesn't have the same relatively short servicing interval, may be that's a better choice for street car?

it's about the same (if not, longer like 50k).. good maintenance of changing the fluids helps as well. The LSD wont get so beat up if you do a lot of daily driving on highways.. if you are doing a lot of track sessions and such, you might want to get it serviced every 30k.

 

very seldom that you would have to swap out a stock LSD (assuming most are viscous anyways)... I cant imagine people needing to take apart their stock LSDs every 100k miles..

 

I might even go through the 1.5 way myself.. a 2-way is a real scary drift-setup for hard/heavy turn-in.. A 1-way might be a good thing for us to have in a daily driven car since it will promote some more understeer if the rear springs are soft, rocking the rear end down and lifting the rear end up.. it's also easier to fix understeer.. at least with a 1-way, you can put a little more power down on the outside tire through a turn rather than the open front spinning that inside front tire and not "pulling" the car where it needs to be.

 

I just found out that Cusco do have optional 1-ways for the GT, but I am not sure if that the Cusco 1-ways work on our USDM cars (since Cusco parts are all JDM)... I'll have to get a hold of Racecomp to see if the 1-ways work on the USDM cars.

here's the link for the info in english.

 

http://www.cusco.co.jp/english/e_cont.html

http://www.maz-sport.com/cusco/lsd.htm

good info. Keefe,.. why dont you start a group by on these.

some more info of what you want to read up on prior to the type of LSD you want to have:

 

http://en.wikipedia.org/wiki/Drifting_(motorsport)

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

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

 

http://www.cusco.co.jp/05_ctg/5lsd_pdf/lsd_112.pdf

 

the more I think about it, the more I want a new center diff than anything. I just want to transmit more torque to the rear and make the car just drift around stuff and make it feel more like a RWD.. it's a no-brainer for me to just straighten out the wheel and mash the gas to get the car to sit straight and just shoot me out of a turn.

I think adding a front 1.5 LSD would help you just achieve that just as much.

good info. Keefe,.. why dont you start a group by on these.

 

 

not everyone wants an LSD of the same type.. especially when everyone have different interests of what they want to do with the car as well as the style of driving..

 

1-ways will make both wheels (on the same axle) spin together as much as possible (depending on the cam angle and limited lock-up percentage) when you mash the gas. Once you are off the gas, the LSD will unlock itself and allow the two wheels spin freely on their own. This is excellent for straight acceleration (such as burnouts) and coming out of the corner and get both tires to spin at the same rate.. [as we all know when making a turn, the inside wheel travels a smaller radius than the outside wheel, therefore, we dont want the inside wheel to spin faster than the outside wheel]. Open differentials (like our front ones) do just that by sending the power to the least amount of resistance [such as a wheel in the air] and wasting all that power that we could use to propel the car forward. So in this case, LSDs don't neccessarily add or take away understeer, it's based on the condition of when you apply the gas and how the tires gripping. For the rear 1-way, it can oversteer the car, for the front 1-way, it can understeer your car.

 

1.5-ways will make both wheels (on the same axle) spin together as much as possible in both mashing the gas and off of it.. the ".5" is the lesser effect of a full decelerating effect. This is definitely good for those people that coast through a turn and giving the car more stability (understeer) when braking.. both left and right wheels will want to go at the same speed thus making it harder to turn, but again, this will vary on other parts of the LSD such as number of clutch plates, the angle of the cam and lock-up percentage.

 

2-ways will lock up the wheels (on the same axle) regardless if you are on the gas or not. This is normally used for RWD cars to get that big angle drift.. think of it as pulling your e-brake lightly right before a turn [which simulates the deceleration side of the 2-way LSD] and the wheels just want to spin an an equal rate regardless without needing to hit the brakes (since it's slowing both tires down at the same rate when going into a turn, whereas in a turn, the outside wheel will always travel further than the inside wheel). Any differential that is in a lock-up situation for that axle, it will want to go straight. So for the RWD guys that get the 2-way, they have their rear wanting to go straight, but the front wheels are guiding them in the direction that they want to go.. the drift continues because the rear axle is spinning as one equal unit, which pushes the front axle (the pivot point) around and around (hence a doughnut) and counter-steering comes into play to prevent the backend from catching up with the front end's radial travel.

 

 

I guess IMO, a really fast setup for an AWD car would have some kind of 1way to 1.5way up front, a torque-sensing center [helical] (of a fixed split of your choice.. I would prefer 25%/75%, but most Cusco center diffs come out of the box at 35%/65%), and a 2-way rear.

 

Of course, all of these LSDs would be clutch/torsen/planetary-gear types (mechanical) and will need more care with the tranny oils. I think the Torsen types are more care-free (so long as you break them in properly). Viscous (like the rear and center that we have on our cars now) are low maintenance and are cheaper to deal with (since tranny/diff fluids can be just as expensive as syn motor oil), but you dont get the direct-faster reaction/performance as the mechanical types.

I completely agree, but maybe 5 people out of this site would. Just an idea

I would like to look up and see if I can cram in a 2-way rear instead.. but I'll have to look up and see if they offer just a 1-way up front.. I am sure many of us dont need anymore understeering on the car

I installed ATS carbon 1.5 ways front and rear in my JDM 6mt as a good trade off.

 

http://www.a-t-s-usa.com/ats-products/lsd-carbon.shtml

 

They do require ~200 mile break in oil change .

Anyone know would the cusco one fit for 5EAT GT 2005?

 

Because from RallyTek website, I read something like this:

 

Cusco Front LSD for 5MT transmission. Adds traction exiting corners. Featuring high tension chrome molybdenium steel housing and gears the Cusco LSD is up for the task of serious competition. With large oil windows for increased flow and Cusco's original groove cut technology for improved efficiency on the clutch plates.

 

Cusco Rear LSD fits all late model Subaru. Adds traction exiting corners. Featuring high tension chrome molybdenium steel housing and gears the Cusco LSD is up for the task of serious competition. With large oil windows for increased flow and Cusco's original groove cut technology for improved efficiency on the clutch plates.

 

Fits all means for Automatic too? Can anyone confirm that? Thanks

I think the autos use some other types of units up front and center.. not sure if there's a specific set up for the autos.. will have to talk to the cusco rep to see if they have a specific application for them.. you can call up http://www.napsusa.com since they are a direct cusco distributor/dealer.

Please my brain is bleeding:icon_surp

Hello,

 

The biggest problem with the cusco center diff is that it's an open diff. Really bites the big one if you ever get wheel spin. We gave up on it after trying to fight the open diff. Cusco should have made it an LSD.

 

I haven't used the front or rear cuscos but I have used Quaiffe and we love them. We also used KAAZ but I couldn't tune out the understeer that the KAAZ front caused. Even at 30% lockup, it was just too much understeer. The Quaiffe solved that problem completely.

 

That said, I know the Locks are experimenting with various diffs and have installed KAAZ diffs front and rear in their LGT and WRX. The LGT is going to Grand Am spec again and then will come back to USTCC spec in time for the USTCC race in Utah. Might be interesting to hear what they come up with...

 

Joel

Hello,

 

The biggest problem with the cusco center diff is that it's an open diff. Really bites the big one if you ever get wheel spin. We gave up on it after trying to fight the open diff. Cusco should have made it an LSD.

 

I haven't used the front or rear cuscos but I have used Quaiffe and we love them. We also used KAAZ but I couldn't tune out the understeer that the KAAZ front caused. Even at 30% lockup, it was just too much understeer. The Quaiffe solved that problem completely.

 

That said, I know the Locks are experimenting with various diffs and have installed KAAZ diffs front and rear in their LGT and WRX. The LGT is going to Grand Am spec again and then will come back to USTCC spec in time for the USTCC race in Utah. Might be interesting to hear what they come up with...

 

Joel

 

Hey Joel,

 

So you have tried Quaife LSD? Do you know if it will fit automatic?

I checked Quaife website, I don't see them have any application for Legacy.

I am very interested in getting one to replace the viscous LSD.

 

Thanks

 

By the way, this is the link I got from Cusco.

http://www.cusco.co.jp/05_ctg/5lsd_pdf/lsd_134.pdf

 

Cusco has all the applications for subaru except for ABS equipped models.

(WTH, all new subaru comes with ABS, Why is that? Anyone knows?)

 

Thanks !!!

Hello,

 

I have used the Quaiffe, but, honestly, I've never looked inside an automatic transmission box in my entire life I have no idea if they use the same diffs in the Subarus. I would assume so?

 

As for the Legacy versus the WRX, I _believe_ but am not certain, that the difference is simply the existence of stub axles. If the diff doesn't have stubs you just need to add them. So between a Legacy and a WRX, the diffs _should_ be interchangeable with the addition of stubs.

 

I would ping the Locks if you need specifics. Steve Lock recently told me that they did a series of diff swaps - going from stock to kaaz in the LGT and from quaiffe to kaaz in the WRX. They should be able to tell you where they picked up the stubs from, what work was involved, etc.

 

Joel

Thanks Joel,

I guess I have no luck, I already check with ATS, Quaife, Cusco =(

All wont fit into automatic (Manual only)