What type of Diff for road racing?
 

My stock diff in my T2 is going out. I see that most people upgrade to a KAAZ 1.5 diff and that is my plan as well. I understand the difference in 1.5 and 2 way differentials, but then I hear that a torsion dif is best for road racing.

what is a torsion dif? how is it better?
is there someone that sells them for the T2?
Can anyone inform me or point me to a good resource?

Thanks for your help
Nick

You can use the FD torsen diff in a T2 housing. The clutch-type KAAZ will hold high hp/tq a little better but the torsen should be smoother and easier to drive.

http://www.torsen.com/general/genera...rential%20work

thanks for that info. Is it "easy" to get a new/rebuilt FD dif?
How much HP and road racing before the FD dif needs to be urgraded?
I guess what am would really like to know is, what do the FD guys do when they want to upgrade their dif?

Comically some people go for the T2 clutch-type, and others go for the Cobra IRS from a Mustang.

I think unless you are making ~350+tq you are not in any danger of killing either of the stock type diffs.

i am ballparking 350hp... not sure on the tq tho.
Thats funny that people "upgrade" an FD with t2 parts... maybe the oil cooler, but not much else!

I was able to find a distributor for the Torsen diff, but no price tag?? not only that, I am not really sure which model I would be looking for.
http://www.franklandracing.com/strtdiff.htm

The Kaaz 1.5 is $900, what am I looking at for a NICE FD or a Torsen T-2?

Or more importantly, can I order a FD dif from a distributor somewhere?

Are any of these from the Mustang?
http://www.northparkmotorsports.com/...eywords=Torsen

You can't use the Cobra IRS on the FC, at least without alot of fab work. There are several cradles for the Cobra IRS onto an FD available which is why it has become increasingly popular.

Basically your options for the FC are: Stock LSD, KAAZ or other aftermarket clutch-type, FD torsen (can get them $300-400 used).

My suggestion if you are only making ~350hp is to either rebuild your stock T2 LSD or buy the Kaaz.

IMO look to a clutch type diff. Maybe Kaaz or a properly setup FC diff. The Torsen has one large weak link and that is that it will unload and go open if one of the tires comes unloaded. That's easy to do if you make regular use of curbing. The other upside to the clutch type is that you can tune the characteristics of it to suit your needs. The downside to the clutch type is that it does wear and will need maintenance. Depending on how often you compete expect 1 to several seasons before rebuild.

I have no direct experience with the FD Torsen but the ones that came in the Miata suffer from a lubrication problem that generally makes them short lived when used for serious racing. That diff is also not rebuildable. So when it breaks it's broken.

+1 for the kaaz 1.5. im loving that setup on my 450 hp track car! i got mine from turbogoods.com. neukin the owner is a vendor on here and mention rob sent you and he'll hook ya up!!

thanks guys. this is the direction and info I was looking for. I'll stick to the original plan and go with the Kaaz 1.5.

I have the kaaz 1.5 and my car is making 510rwhp to 565rwhp depending on boost, the diff is great! I have no problems with street or track.

IMO clutch type is the way to go...it involves you working on your car more, yes. But you know what its going to do every time. And its really not that hard to rebuild them.

The OS giken's will outperform and outlast the Kaaz units, and you wont be needing to drive in figure 8's to break it in. Much nicer better engineered units.

How will it out perform the kaaz unit? I'm not saying this because i own the kaaz but would like to know what it does different?

Since release in 00, there have been ZERO failures of a production unit, and ZERO rebuilds necessary at any level, from street use to professional racing. Not too bad.

Billet and Heat-treated case is not found on most competitors’ units

Forged internals, and RAW-forged gear teeth (strongest gears available anywhere)

More disks+larger disks = more friction surface area to dissipate heat and allow true 100% locking capability. OS units typically house TWICE as many disks as competitors units (up to 28+ plates)

Take a look at the first pic; OS unit is on the left, and a Kaaz unit is on the right… look at the amount of disks each can hold, huge difference.

Ultra-precise disk machining, which means the unit is ready to perform immediately after installation… NO BREAK-IN PERIOD REQUIRED!

Non-intrusive cone spring design prevents unnecessary wear and results in consistent and reliable performance over the long-term.

100% locking and unlocking capability: True 100% lock results in no moving components= no heat generation. The main reason other limited-slips fail is because too much heat is generated, since true 100% lock cannot be achieved.

OS has yet to see one of their Super-Lock LSD’s fail in the field again not too bad.


If you look in the second pic the KAZZ unit is on top versus the OS on the bottom.

Look at case coloring showing heat treatment of one, versus the other with no heat treatment.

Look at number of discs

Look at the cone springs on end the OS design is smaller and the case shape allows it to escape the heat and pressure generated by the disks.

If I had to pick a diff for road racing and my choices were KAZZ or OS I will take the OS stuff. Not knocking your choice I used to sell the KAZZ units and still will to those who insist on them. But OS is what will be in my car.

Very notable difference in design and construction.
have you used this diff on any road course yet? any difference when driving?

What's a good source in getting an OS unit here in Cali? What do they cost?

what about cusco?

Just received word from my friend in Osaka that at the last 7 club race the Pan Speed Rx7 Placed 1st in the time attack utilizing the OS giken unit. Impressive enough he said it was pushing over 500hp. I would be interested to know what the cost of the unit is.

What companies are selling cradles for Cobra IRS' for FC's? I have family members that work at Ford shops, so Cobra stuff could be cheaper for me.

i have a Cusco 1.5way RS kit in my FD and it's been great for track days and autocrossing. its a bit hectic on the street, due to the crazy amounts of clunking at low speed corners. then again, what track built FD isn't hectic on the streets? do all diffs clunk at low speed corners?

unfortunately i dont have any race experience on my stock diff for comparison, but i love the way my car pulls and connects around corners now. from basic on-ramp comparisons from years ago, the car feels much better with the Cusco LSD; which is to be expected.


not to hi-jack the thread, but i have my stock torsen FD diff. PM me if you would be interested in buying it.

Been driving open wheel diff for quite some time and I cant wait to feel the difference in handling and launch with an after market LSD.

I'm in a similar position. My car is an 89 GTX with an open diff because it was automatic and n/a. Now it's a HBP T2. I bought a brand new LSD clutch-type diff from Mazda and now I'm looking for axles and I'm debating if I should get an LSD unit. Either KAAZ or Mazdaspeed.
But my question is: How much hp or trq can the stock S4 T2 axles take ?

meaning how much hp or trq can the stock S4 T2 axles support until they brake

http://enjukuracing.com/giken-super-...91-p-7967.html

from enjuku its $1390

looked around and prices vary from 1320-1400 range so its best be worth it, this would definitely be a great upgade...