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Well its come time to figure some things out about center diffs......

I really want to upgrade my 5MT out a 2001 Impreza RS's center diff.

From what i can find there is not much options here:

http://www.rallispec.com/dif_gls_rst1215.html
http://www.cusco.co.jp/en/parts_product ... _gear.html

I see the STi 20kgf Center Viscous LSD RST-1215 will work on my trans BUT from what i read its very bad on the street and auto X. So thats not soo good for what i want to do.....

The Cusco tarmac seems to be the best option here BUT i cant find any dam thing about the thing! Also where to buy it?
Any one know something i dont???

I know there is the RST-1212B sti center diff BUT that for the 98 and down transmissions....

Any input for anything would be nice!

Note: i mainly want to this "mod" because my transmissions transfer gears and bearings are toast.
So when im in there i should swap out the center diff.

From what I've read in my differential research (and I've read quite a bit because the standard 5MT really doesn't offer adequate torque biasing for higher than stock WRX power levels IMO) the Cusco tarmac gear is an open differential with a 35:65 torque split. It's recommended that you have a front and rear LSD when using it competitively, otherwise you can wind up sending nearly all of your power to a single wheel with low traction (vs. at least 1 front and 1 rear wheel with a center LSD and open F/R diffs). As for where to buy it, it's not an option I considered for myself with it being open so I never looked that far. But from what I've read of people who've had it, most seemed to really like it. Sounds like it oversteers a lot, and God knows us Subie drivers love oversteer, lol.


I personally want to find a 5spd DCCD to throw in (cheaper than a 6spd, and no real conversion necessary aside from the addition of a DCCD controller). 36:64 torque split with adjustable lock and certain boxes even have a helical front LSD. Really hard to beat, even if you throw $3K worth of LSD's at the stock 5spd.

Also, aren't you able to swap a phase I tail housing onto a phase II trans? Couldn't you do that to use the 12KG center diff? I think I remember reading about that.

The Cusco diff is long out of production but they do come up for sale now and again. I managed to score a dccd 5-speed for 850, and that isn't too much more than I've seen the diff go for.

Toronto's where most of the importers are, you could put in a request for specific parts if you wanted.

Honestly, why waste the money? Unless you are just spending money to spend money? You will see better gains with diffs on the front and rear. I have cusco 1.5 way on the front and rear of my rally car. Transforms the way the car puts down power on the loose stuff. Still a stock center diff. I'd love to upgrade it, but right now even running near the top of the pack (starting 12th on the road out of 60 cars at national events) I still don't feel like the center diff is holding me back or anything.

It really is an upgrade that is a huge waste of money unless you already have the talent to actually exploit it. Otherwise unless you have a DCCD with a programmer, it's just going to make the car feel worse.

Ya actually just scrap your subie and buy a lotus.

MConte05 wrote:.

It really is an upgrade that is a huge waste of money unless you already have the talent to actually exploit it. Otherwise unless you have a DCCD with a programmer, it's just going to make the car feel worse.

It is impossible for me to imagine the car feeling worse with a tighter center diff than with the stock unit. But I guess that depends on how you're looking for it to behave.

I love my 35:65 power split

James614 wrote:

MConte05 wrote:.

It really is an upgrade that is a huge waste of money unless you already have the talent to actually exploit it. Otherwise unless you have a DCCD with a programmer, it's just going to make the car feel worse.

It is impossible for me to imagine the car feeling worse with a tighter center diff than with the stock unit. But I guess that depends on how you're looking for it to behave.

Because it starts to bind on the street, premature wear, and general suck. Even with my tighter front/rear diffs tight turns on pavement cause the car to jump around. A stiff center diff would make it even worse, and if his car is primarily street and occasional autoX then a stiffer center diff is about the worse thing he could do.

However a proper DCCD with a good programmer is a fun upgrade. Just trying to discourage putting a permanent diff into a street car. There is a reason they are mostly motorsport use only, otherwise just burning money up.

Ya actually just scrap your subie and buy a lotus.

Good advice!

Mine is going up for sale soon. I want to spend more money on racing a shitty legacy.

Do you have the RS or MZ diffs? Cusco claims the RS has lower initial torque and won't bind on the street like the MZ does. Never been able to confirm how true that is though.

Mine is going up for sale soon. I want to spend more money on racing a shitty legacy.

:O but what then will you tell all the ladies!??

My wife is convinced I won't go through with selling the car. I might pick up a Fiesta ST to live with for daily driving for a year or two until the Lotus Evoras come down in price a bit more.

Well aside from most of the useless comments here, i still see is some value hear.


So the cusco diff is basically out of the question. Unless i want a used unit. No thanks. I have replaced way WAY to many center diff already in my life. The only trans i have NOT replaced a center diff on is a STi 6MT.

The 5MT DCCD does interest me though.
I would prefer NOT to have to swap my gearbox again tho! Maybe 4th times a charm?

Has anyone had a 5MT JDM phase 2 gearbox apart?

I would basically just be in it for the center diff.

And DCCD is cool and all but i just want a more rear bias legacy.

Does the JDM center diff have a default split of 35-65? like the STi 6MT?
Or is it a 50-50?

If so i would TOTALLY just do some part swapping.

Although! How much work one have to do swap a old phase 1 extension housing to a phase 2 trans? Then i can run a 12G!

My dccd 5mt is 35:65 biased. It is a blast to drive

Hmmmm well thats good to know that the 5mt with DCCD have a default 35-65 split!

Tho from what i have seen from the googles, you cant just stuff in the center diff.....

The diff has a large magnet on the front part of it. I dont even think you can even swap the entire extension housing..... I dont see it anyways......


Looks like i might just need to buy a STi 20kgf center diff.....

Do what you want, but no-one is going to encourage you to spead the money on something that will 1. Cause you to understeer all the time, and 2. Burn out fast when used on pavement.

The dccd part can be swapped from tranny to tranny. Mine is from a ver6 sti-ra and is phase ii. It doesn't need a controller to use, all that does is control the amount of lockup. The center diff is mechanically and permently set to 35:65 split.

Well mike-tracy, i KNOW see what you mean by swappable.

I was looking at the 5mt dccd center diff BACKWARDS!!

I though the big @ss magnet was infront of the center diff support bearing!

Its not!

So as you said it its TOTALLY swappable into my 2001 RS trans!

So now the question is DCCD was frist offered in what ver. of STi? V5 or was it V6

Also

Thanks mike-tracy!

It was offered in phase I trannies as well. I know ej20k based GC's got it (ver 3-4). Not positive about ver 1-2.

Now before you get too excited, almost no GC's got dccd tranny. Matter of fact, even JDM GD Sti's could be ordered with or without the dccd (even tho all of those got a 6mt).

Here is the best list available on Subaru trannies

Http://forums.nasioc.com/forums/attachm ... 1303880549

If you are looking for a phase 1 trans with DCCD, look for the wire coming out the top of the small flat plate on the tailshaft. No wire? No DCCD.

FYI-A phase 1 complete center diff, and housing will work on a phase 2 transmission/gears. This also works with phase 2 center/housing and a phase 1 transmission case and gears. It only works with the complete center diff and matching housing. I have done this twice now with no ill results.

I do have a STi RA DCCD/trans in my wagon. I bought a standalone controller from DCCD-PRO. I made a plug and play harness to the switch with the harness off of the STi body harness. I mounted the controller computer underneath the center console.

Out of curiosity, how much are you paying for the 5MT DCCD center diffs/transmissions?

I agree. i would like to know how much this gear box/ dccd center diff would cost.

My plan was to run RA gears in my 01 RS trans anyways. This just might be cheaper in the long run.

I guess what I'm trying to see is, depending on the cost of the DCCD center diff for the 5spd and/or specific box, you're still at the limitations of the 5spd trans. If you're close to the cost of a 6spd, I don't see why you wouldn't just go with the 6spd. There are a few little things that need to be done to get it in, but honestly, it's really quite easy.

I've seen the transmissions go for nearly 1/3 the price of a 6spd, though it does seem the importers and JDM vendors think anything anything with a DCCD knob is worth its weight in unobtanium.

The only way I've seen a 5mt dccd sold was in a tranny.