818 Transmission upgrades

[sandmantm]

I am planning a street 818S build using a 2007 WRX wagon as the donor. I already plan to have a limited slip differential installed. I am curious if the axles need to be upgraded? On the no side, the 818S weight is only approximately 60% of the donor weight. On the yes side, with the AWD in the donor the front axles only transmitted approximately 50% of the torque and will obviously have to transmit 100% in the 818. I am likely to push the engine to approx 300 HP. Thanks for your input.

http://www.driveshaftshop.com/import-axles/subaru/subaru-2004-2007-wrx-2005-2007-sti-gd-sedan-750hp-level-5-front-axles

[philly15]

LSD is a great idea and are we talking 300 hp at the flywheel or to the rear wheels? even at that power level i dont think you will have any issues with the axles, out of all the crazy builds on wrxs/sti's my friends and I have done i dont think any of us had had any failure with the axles and we are talking power levels double what youre shooting for differentials on the other hand is a different story a front LSD is a great upgrade and one i plan on doing i would just use the wrx axles until there is an issue unless you can afford it in your budget go for it

[Mechie3]

FFR is providing custom axles with the kit.

[sandmantm]

Thanks much for the input.

[philly15]

FFR is providing custom axles with the kit.

really? didnt know that good info to know!! thanks!!

[RM1SepEx]

you use the front axle's inner cv joint and the outer joint from the rear axle with their custom rear axle. In the front you use the stub from the outer cv to hold the wheel hub together with the front bearing assembly.

My 05 5 speed should be comleted next week. The transaxle was dropped off last week for Quaife installation.

[longislandwrx]

Slightly off topic but did anyone at sema see how the clutch assembly linked to the slave cyl? Did they just run a hardline to the back and a small piece of flex on the trans?

[Bob_n_Cincy]

13650
Slightly off topic but did anyone at sema see how the clutch assembly linked to the slave cyl? Did they just run a hardline to the back and a small piece of flex on the trans?

No lines were run on the go kart. Couldn't see anything on the R or S.
Since the engines moves, you need a flex hose somewhere.
Bob

[flynntuna]

It does seem like the best way to go, good idea.

[rjh2pd]

For the transmission upgrades, are you guys going to up the gearing in the car? If so where at?

[Rasmus]

For the transmission upgrades, are you guys going to up the gearing in the car? If so where at?

I plan to up the gearing by using a 2005-6 Legacy GT transmission. The gears come evenly spaced. 4.111 final drive. To help out even more I'll probably run smaller than WRX diameter tires.

There's also the 2005 Outback XT transmission. Same gears as the Legacy GT but with a 4.444 final drive.

Manual 5spd
1- 3.166
2- 1.882
3- 1.296
4- 0.972
5- 0.738
final 4.111 or 4.444

[C.Plavan]

Are there "Real" LSD's for these? I'm not looking for Torque Bias, or Quaife type LSD units. I want a Real LSD with Decel lockup also (Anything but OS Giken- Complete crap LSD's BTW). Any leads?

[philly15]

Are there "Real" LSD's for these? I'm not looking for Torque Bias, or Quaife type LSD units. I want a Real LSD with Decel lockup also (Anything but OS Giken- Complete crap LSD's BTW). Any leads?

Cusco makes a 1.5 way diff. For the wrx I believe kaaz might as well

[Rasmus]

Any leads?

Kaaz makes one (http://www.kaazusa.com/lsd_subaru.html) they market as a 1.5 LSD.

From their marketing department:

Different Type of LSD Configurations (1 Way, 1.5 Way & 2 Way)

Some manufacturers make LSD's in different configurations and are commonly classified as 1 way, 1.5 way and 2 way. This designation reflects the design of the cam groove which enables the LSD to function differently under different loads. A 1 way differential means that the cam is shaped in such way as to have positive lock only when accelerating. The 2 way is constructed in a way to have positive lock motion in both acceleration and deceleration mode (Figure 3). The 1.5 way functions almost same as a 2 way but provides less lock when decelerating. The 1.5 way can provide more forgiving balance when braking than a full 2 way setup, although it is less effective for true racing applications, it provides easier operation for beginners in throttle off conditions. 1.5 way is also very effective for front wheel drive cars which need extra stability during braking.

I don't know anything about this product other than it exists.

MFactory also makes one - Helical LSD Subaru WRX/STi GC8 - Front PART #: MF-TRS-05WRX Don't know anything about this one either.

[Rasmus]

RE: LSD Just found the Cheap and Effective TorSen Front LSD for Subaru 5MT thread (http://thefactoryfiveforum.com/showthread.php?3899-Cheap-and-Effective-TorSen-Front-LSD-for-Subaru-5MT) on this very forum.

[Rasmus]

Okay. Bin all that I just typed, and get a STi Helical Front LSD from a JDM 5-speed transmission. It's OEM and you can set it up in 1.5-way or 2-way bias.

http://farm5.static.flickr.com/4150/4954056192_ae2afb3dcb.jpg

http://farm5.static.flickr.com/4152/4953469105_ab615b5941.jpg
Apparently you change from 1.5-way to 2-way by switching the position of the gears from the left opening to the right in the above photo.

EDIT: I can't confirm that this LSD can be switched from 1.5 to 2 way. Have to mark this a rumor. It may be a way to switch from 1-way to 1.5-way but I can't confirm that either. I don't know what's true here.

[C.Plavan]

Okay. Bin all that I just typed, and get a STi Helical Front LSD from a JDM 5-speed transmission. It's OEM and you can set it up in 1.5-way or 2-way bias.

http://farm5.static.flickr.com/4150/4954056192_ae2afb3dcb.jpg

http://farm5.static.flickr.com/4152/4953469105_ab615b5941.jpg
Apparently you change from 1.5-way to 2-way by switching the position of the gears from the left opening to the right in the above photo.

Need the part number on that. Good find.
I also contacted a friend of mine who owns Guard Transmissions- He has not made a 5 speed STI "Real" LSD in 6 years. He says it may be time to bring them back. I use them in my Porsche race car. Top notch quality and built to last. If you are racing, do not wast your time with the 1-1.5 way units.. But if you are racing, you probably already know that.

[Rasmus]

He has not made a 5 speed STI "Real" LSD in 6 years.
Could you define what you mean by "Real"? Because No True Scotsman (http://en.wikipedia.org/wiki/No_true_Scotsman) knows what you mean. =)

[C.Plavan]

Could you define what you mean by "Real"? Because No True Scotsman (http://en.wikipedia.org/wiki/No_true_Scotsman) knows what you mean. =)

Real- Meaning not a 1 way or 1.5 way- Real LSD in a racers eyes are one that lock up on Decel also, not "sort of lock up" :) . They are more stable in trailbraking in high speed corners. Crucial in a rear and mid engine car.

[Rasmus]

Because I can't confirm that the JDM LSD pictured above can, in fact, be switched to 2-way, I added an EDIT to my post. Going to have to call this one a rumor until we get more evidence.

[Jodie]

I'm using a borgwarner 3103 8.28:1.
brand new siemens 5135
13748

[Xusia]

Using it for what? What IS it?

[JeromeS13]

Looks to be an electric motor.

[PhyrraM]

Keep in mind that virtually all of the LSDs designed for the Subaru transmission were designed for use on the front (steering) wheels. In the 818, it is now the rear, driving wheels.

The proper "real" diff for your needs might not yet exist.

[RM1SepEx]

Using it for what? What IS it?


My guess:

motor, transaxle (single speed I assume), controller on the top

volts, amps?

[Rasmus]

The proper "real" diff for your needs might not yet exist.

The few hours of online research I've done, leads me to believe that this is the case. The best 5mt "Front" LSD I've been able to find is a 1.5- way. No 2-ways (only rumors), and not a single clutch-type.

[PhyrraM]

Not suprising, a true locking diff (or even a tight LSD) would absolutely kill turn-in and steering feel (in an actual Subaru).

It's easy to overthink this. Keep in mind that on such a light car, with a relatively short wheelbase, the "tighter" an LSD is the more the turn in is going to suffer. As long as FFR does it's job with the camber curves and suspension tuning to maximize the contact patch - most would be suprised how effective an open or lightly 'packed' LSD can be.

[Rasmus]

My ambitions to bang off the curbs are dashed. DASHED!

http://media.racer.com/images/2012/10/16/surf3_308511.jpg

[C.Plavan]

Not suprising, a true locking diff (or even a tight LSD) would absolutely kill turn-in and steering feel (in an actual Subaru).

It's easy to overthink this. Keep in mind that on such a light car, with a relatively short wheelbase, the "tighter" an LSD is the more the turn in is going to suffer. As long as FFR does it's job with the camber curves and suspension tuning to maximize the contact patch - most would be suprised how effective an open or lightly 'packed' LSD can be.

With all due respect, I will have to disagree with you 100% on the "Tighter" LSD comment. One of my race cars has a 89 1/4" wheelbase (~6 inches shorter wheelbase than the 818R), Rear engine, ~2080 pounds (with me and all fluids) and a 37/63 (F/R) weight distribution. It has a full 2 way "tight" racing LSD with 211 RWHP. A LSD will not absolutely kill turn in and steering feel. Just like ANY race car, you can dial out understeer if you know what you are doing. Especially, with a decent suspension design which the 818R will have.
Now if you are only doing Autocross stuff, it is a known fact that the 1 way LSD (Quiafe) will benefit you more.

But don't take my word for it- :)

http://www.youtube.com/watch?v=EokoS6R_6c8
http://www.youtube.com/watch?v=EokoS6R_6c8

[PhyrraM]

I was not refering to a track-only, purpose built race car. I was refering to a real-world, live with it every day, reasonable ride, and most importantly - predicatable- street driven 818S.

[jaso]

A LSD will not absolutely kill turn in and steering feel. Just like ANY race car, you can dial out understeer if you know what you are doing. Especially, with a decent suspension design which the 818R will have.

The first part of PhyrraM´s post with the strong words ("absolutely kill turn-in") was surley refering to the front LSD in a Subaru when it`s acually used in a Subaru.

The second part was about the 818 application (when the "front LSD" acually will be used in the rear). No strong words in this part. Just som carefully thinking from him about how it actually not need to be a bad idea with the now available front Subaru LSDs (or none at all) after all.

It makes sense to me anyway :).

[C.Plavan]

The first part of PhyrraM´s post with the strong words ("absolutely kill turn-in") was surley refering to the front LSD in a Subaru when it`s acually used in a Subaru.

The second part was about the 818 application (when the "front LSD" acually will be used in the rear). No strong words in this part. Just som carefully thinking from him about how it actually not need to be a bad idea with the now available front Subaru LSDs (or none at all) after all.

It makes sense to me anyway :).

Now that we know he was talking about a street car, it's null. I was in race mode when I typed that.

[Rasmus]

Now if you are only doing Autocross stuff, it is a known fact that the 1 way LSD (Quiafe) will benefit you more.

Could I get more explanation for this in regards to a Mid-Rear Autocross car? Links too if you've got them.

[C.Plavan]

Sure Rasmus-
If you are autocrossing, as you know, its relatively lower speed with tons of tight corners (compared to a racetrack). You will not need the benefit of the "lock-up" of a 2 way LSD on deceleration. Since you have so many tight corners, without high speed trailbraking sweepers/corners, a "Torque biasing" LSD would benefit you better. That is, if autocrossing/street driving is all that you plan on doing.
You could use a 2way LSD if the lock up ratio/ramps were lower than say a race spec LSD. My racing LSD is 50/80.

Here is a good source of info from Guard Transmissions- Keep in mind they usually only make Porsche LSD's, but they do have some 5 speed WRX Torque Biasing on the shelf too. I have talked to Matt, he says he may dust off the 2way LSD model again for the WRX for me. He will have a market for the 818R racers. Their stuff is bulletproof.


Frequently Asked Questions


How do I choose a differential for my vehicle?

The most typical installation choices for our differentials are as follows:
(a) Street / autocross - Torque-biasing suitable for most applications, especially autocross. 40/60 (or 40%) LSD for all Turbo and high-performance street cars.
(b) Street / track - Torque-biasing for light track use, with stock suspension. 40/60 (or 40%) LSD if car has stiffer suspension or power upgrades.
40/60 (or 40%) LSD for any car used primarily for track.
(c) Track only - 50/80 LSD Special order “Zero-Preload” LSD, with 4, 6, or 8 friction discs




Limited-slip differentials provide lock-up on both acceleration and deceleration. The amount of lock-up on accel and decel can be adjusted by selection of the internal plate sequence and/or ramp selection. Lock-up on deceleration allows late braking and aggressive entry into high speed turns, reasons why all professional Porsche road- racing teams utilize LSDs, rather than TBDs.




Torque-biasing differentials provide lock-up on acceleration only. The amount of lock- up increases as the amount of torque increases. On deceleration, lock-up is negligible, making the TBD ideal for the slower-speed turns of Autocross. (In the same slow speed turn, an 80% LSD would most certainly cause unwanted understeer.)


A torque-biasing differential performs like an open diff whenever one of the drive wheels approaches lifting off the ground. Lock-up and traction are lost until both drive wheels are again planted firmly on the pavement. Distinct limitations exist when a TBD is incorrectly used in a rear-engined or high speed track race car.
A great deal of confusion is caused by optimistic sales information distributed by companies that only offer torque-biasing differentials, or when a TBD is described by a vendor as a “limited-slip differential”. As Guard offers both differential types, we try to present as much information as possible, so that an informed choice can be made based on suspension set-up and intended use of the vehicle. Too often, we have seen the full potential of a car severely limited by use of the incorrect differential type, or by a low quality Chinese knock-off “LSD” that fails to provide long-term performance.
Thank you for your interest ---
Paul Guard

[Rasmus]

My primary use with my 818R will be autocross. >90%. There will be a track-days and a group-drives on occasion. If I installed a 1.5-way torque-biasing differential would I be a happy man?

[Turboguy]

So- a 1-way LSD functions as a locked diff while under acceleration and a 2-way LSD will lock under acceleration AND deceleration equally? Is that correct?

Does this mean a 1.5-way works under both acceleration AND deceleration but at different locking rates? (specifically a deceleration lock rate that is half what you see under acceleration?)



One thing I am concerned about with the 818 is the dreaded "drop throttle over steer" issue that mid and rear engine cars seem to be famous for.

Although I've never tracked one, I have read that Porsche seems to have cured (or minimized) this tendency in the last 2 iterations of their 911. Is anyone familiar with what changes they made to improve the car's drop throttle stability?

[Racebrewer]

"One thing I am concerned about with the 818 is the dreaded "drop throttle over steer" issue that mid and rear engine cars seem to be famous for."

Isn't that more of a weight transfer issue (taking your foot off of the gas shifts weight forward) than anything? Big fun in a front engine, front wheel drive car when the rear goes scary light and loose.

The 818 will be my first rear wheel drive, mid engine car.

John

[C.Plavan]

You need to pick which LSD you want. You have all the info :)

As far as drop throttle oversteer, just be aware. It separates the men from the boys on the race track :)

I would be more concerned about a mid engine car cornering at its limit. They handle great, but it can bite you at the cornering limit. Think about this, and try it on your kitchen counter. Grab a knife and grab a spoon. The knife is a mid engine car (50/50 weight ratio) and the spoon is a rear engined car.
Spin them.....
It is easier to initiate spinning a knife (mid engine) than it is a spoon (rear engine). When you spin a mid engine car, it happens so darn fast and is harder to recover. The spoon/ rear engine takes more to initiate the spin (its slower-weight in rear) so you can "catch" it when it starts to happen better. Usually what happens is an unexperienced driver feels it happening (spin), then slam on the brakes, or lift. That just makes the event worse and you can't recover from it.

That's why everyone thinks the oversteer is bad in rear engine cars. It's actually a good thing if you know how to use it, and know what to do if you feel it.... Just don't panic! :)

[wleehendrick]

That's why everyone thinks the oversteer is bad in rear engine cars. It's actually a good thing if you know how to use it, and know what to do if you feel it.... Just don't panic! :)

That minds me of one of my favorite quotes: "Oversteer is when the passenger is scared, and understeer is when the driver is scared."