WRX Drivetrain Discussion

[mn_vette]

I've been doing a bit of looking around at the WRX platform trying to dig up info on the pros and cons of this setup, things to watch out for and what not. Here are my thoughts on the matter.

TRANNY:

The first big problem with the WRX is the 5 speed transmission. Hard launches and fast shifting are what typically breaks parts in this tranny from what I've read. This tranny won't handle the stock horsepower if its abused. Given that this new FFR car will not have AWD(and no LSD) and will be half the weight there is a much better chance that this tranny will survive alot better than in the WRX. I guess the general rule is that in the 350+ range is time to upgrade the transmission in a WRX. Half the weight should translate into half the forces on the transmission(F=M*A), or you get twice the acceleration. It will be interesting to see what happens with these transmissions. Make sure your donor has a good one.

Why not just upgrade the transmission? The cost of the transmission upgrade with new, stronger gears is about $6500. Which I'm guessing most of us are planning on spending less than that on our entire donor car.
Transmission upgrade info: http://forums.nasioc.com/forums/showthread.php?t=665334


What about the STI 6-speed transmission? Well, lets just say that the design between the two transmissions are nowhere near the same. The WRX is a mechanical AWD system where the STI is a complex computer controlled, mostly RWD, system. I really don't think there's going to be a way to convert it to 2WD. Here is some info on it. http://www.driveperformance.subaru.com/version1_2/blueprint.asp


An LSD would be a great upgrade for this transmission in 2wd. The WRX has several places for differentials, so while looking for one make sure you find one for the front. But to install it you will, of course, need to tear apart the transmssion to do it.

Here is the part that people are using to change the 5 speed to a 2wd. This place calls it a "subaspool". http://www.subarugears.com/index_files/Page497.htm


ENGINE:
Most WRX's have the 2.0L which is going to be good to 3-400 hp before the lower end starts going bad. Being a V8 guy that seems like an ok daily driver horsepower number to me rather than a real sports car. So I decided to try and get some BALLPARK figures. 1/4 mile being the general performance scale I found this on line calculator that gives us general info. http://www.carforums.net/hpcalc.php

Lets say the new FFR car weighs 2100 with a nice wookie driver. Here are some quarter mile times for given horsepower levels.

Stock WRX: 230 CHP
12.86@106mph

275 CHP
12.1@112mph

325 CHP
11.45@119mph

400 CHP
10.7@127mph

of course these numbers are fully dependent on the driver, traction, aerodynamics of the body, oh and did I mention these are only estimates. But it gives you a good idea of what this car could be capable of.

I think using the 2.5L engine would be a big advantage to this car and you could very reliably run 400 chp and have a great 10 second street car that gets everyones attention. That is of course if the tranny holds together.


If anyone needs to correct the information that I've found or has other thoughts of their own please post them. The more information we have out there the better off we all are. ;)

[thebeerbaron]

My question for all you "V8 guys" worrying about power: (Not to pick on y'all, and mn_vette, I am assuredly not picking on you in particular):

Have you driven a 1800lb car in recent memory?

Have you ever driven a 1800lb car with 225hp?

400hp in a 1800lb car is nowhere near daily driver territory. It is in "ludicrous speed" territory. I doubt most people, including 99 percent of the people posting here, could drive that on a track at its full potential. And to show that I'm not really being a pompous ***, I'll say it right away: I can't.

For a frame of reference: Miata guys with 2400lb turbo cars (fully loaded) putting 250+ to the wheels are constrained by two things: how much tire they can stuff in their wheel wells and the Corvette in front of them (ok, now I'm picking on you mn_ ... but its in good fun). Aero has become a big deal to these track folk. How fast are we talking? Unofficial record last year that I know of was 1:38.9 around Laguna Seca (http://www.youtube.com/watch?v=o906vtS7eFo). See how that compares to these lap times (http://www.fastestlaps.com/tracks/laguna_seca.html). I believe he was in 350hp territory.

You're talking about dropping 300lbs off the car and adding 50hp. Ludicrous speed.

Sure, it would be fun to stuff a 400hp engine in this car and turn tires into smoke. But the 200 extra hp that have you worrying about the transmission are only going to be used to turn tires into smoke - it's not going to be possible to use that power in any realistic manner.

[riptide motorsport]

Im going to build it, going to shoot for 400ish HP, stock tranny. With the weight I expect it to hold up to decent thrashing. If not hopefully the engine removal process will be fairly easy as theses tranny arent overly exspensive so I'll just be replacing trannys!!!!!!!!

[Rotr8]

The first big problem with the WRX is the 5 speed transmission. Hard launches and fast shifting are what typically breaks parts in this tranny from what I've read. This tranny won't handle the stock horsepower if its abused.

This is pretty much true for any car, you dont ever need to abuse a transmission to go fast, if so you dont know how to drive.

[audsyn]

The WRX 5-speed has a bad reputation, but deserved or not it's largely irrelevant to the new roadster. 1000 lbs lighter and 2WD means that the same torque output puts less than half the stress on the gears as it does in the WRX.

WRXs converted to RWD break differentials and axles all day long but not the transmission. A lighter car should reduce that problem, but I wouldn't expect any problems from the trans. Maybe the axles!

[Benji]

This is pretty much true for any car, you dont ever need to abuse a transmission to go fast, if so you dont know how to drive.

Again with this concept that you don't know how to drive if you kill transmissions :)

I've disagreed on it before and I'll disagree on it again. Yes you can get going fast and carry a decent pace whilst being smooth at the same time but, if you want to be the fastest off the line, fastest through the gears, it's not going to be nearly as smooth nor is it abuse, it's just USE. To it's fullest extent.

[PhyrraM]

While the 6-speed has electronic clutch packs in AWD form, when converted to 2WD by locking or removing the center differential all the electric stuff is rendered useless.

A locked up 6-speed will work perfectly fine, no electronics needed.

[mn_vette]

I wonder how much work it would take to rip apart the 6-speed and figure out how to remove the clutch packs and weld together what ever needs welding to get this to work. Its an interesting idea.

BeerBaron, most of us are clueless when comes to a 1800 pound car with several hundered horse. I know I've driven my Dodge neon at 2600 pounds and 150hp(maybe). That's why I wanted to post those theoretical quarter mile times. I think I'll be plenty happy if I can build this car and give it 300hp with a few minor upgrades.

[JRL]

I raced a CSR with similar power to weight ratio. In a word it was - FAST. It was also easy to drive fast had great brakes and cornered as if on rails.

[PhyrraM]

I wonder how much work it would take to rip apart the 6-speed and figure out how to remove the clutch packs and weld together what ever needs welding to get this to work.

Six speed: http://www.ppgearbox.com.au/page.asp?productid=70

http://eng.kaps-transmissions.com/news-kaps/subaru_rwd_conversion_kit_-1057.html

Five speed (for picture): http://www.ppgearbox.com.au/page.asp?productid=72

Even though the arraignment is very, very different, the center diff has the same single input (from the gear cluster) and dual outputs (front axles and rear driveshaft) that a regular rear diff (driveshaft in, 2 axles out) has. And just like a rear diff, if you lock it up by welding or a spool, you can take one of the outputs away without effecting the one still connected.

[Steve91T]

I think the only way you'd break a tranny, even with 400 hp, is if you are drag racing on slicks.

Personally, 300 hp is easy to get, that's what I'd be shooting for.

Steve

[Mauricio]

First post on this forum, I am the proud owner of a Subaru Impreza 2.5RS since new in '00, btw.

I am excited at the prospect of a this new kit, being that it is Subaru powered.

Power/weight x traction is the name of the game. Just ask any Supra guy what the difference between a 400hp supra and an 800hp supra in the 1/4. The answer will most likely, be "nothing, I can't get 800hp down to the ground"

Take your ideal "fast" car and figure it's power/weight ratio and apply that to the target weight of this new kit, +10% . I will agree with those who say that 400hp might be overkill on a car this light. In fact, I hope to have the 165hp N/A engine in my 2.5 swapped out, rebuilt, and ready to go into this new kit. I am sure it will be just as fast as a 400hp car. I know a guy with a Mallet v8 solstice, (400hp LS2?) and he gets sideways in third, in a car that weighs 2800#.



The 5speed in question, has had several things working against it, thus gaining it the "glass tranny" reputation, the majors are:

1. AWD - as mentioned above, 5 speed's in RWD conversions seldom have problems because when you apply too much torque, the tires just break traction, no harm, no foul. What to you do when you are limited by traction problems? Bigger/Stickier Tires! The result? broken half-shafts/differentials.
That same shaft-snapping torque has to go somewhere in an AWD system, and when you have 4 half-shafts working against 1 set of gear teeth, it is usually the later that lose.

2. Drivers - you wouldn't believe the number of times I have read on NASIOC: Hi guys! My parents just bought me this WRX, and it's my first stick-shift car. I haven't gotten the whole "smooth take-off from a light", thing yet, but what's the fastest way to launch this thing? hold the RPM's at 4k and let the clutch out, while flooring the gas so that it stays on-boost, am-i-right?"

I have every confidence that the transmission will be more than adequate for this application.
As with most cars, it's the loose nut behind the wheel that is the determining factor.

M.

[bu11dogg2]

With a well modded 2.0 your looking at 340 crank HP. Add 200lbs driver it equates to a .170 ratio. That's similar to a Lamborghini Murcielago and better than the Mercedes-Benz SLR McLaren.

If you use a 2.5---400 crank is pretty easy to make with a big turbo. You're talking Enzo territory.

The stock 2.0 with stock turbo is .111 which is Porsce 911 Turbo territory.

(all figures based on 2000lbs car)

You can keep your V8.

[bu11dogg2]

this is definitely an interesting article about converting the 5speed to 2wd.

http://www.subarugears.com/index_files/Page497.htm

Not really sure how FFR intends to work around the cost of this conversion if it requires the center diff to be removed.

Also, stock WRX 5 speeds have an open front diff which means one wheel burn-outs when you mash the gas.

A decent front Diff will cost $1000-$1500 and for most will require professional installation. That's $2000.00 just to be able to put the power to the ground.

[thebeerbaron]

Also, stock WRX 5 speeds have an open front diff which means one wheel burn-outs when you mash the gas.

A decent front Diff will cost $1000-$1500 and for most will require professional installation. That's $2000.00 just to be able to put the power to the ground.

When the Elise was released in the US, it was not initially available with a limited slip. The engineers didn't feel it was necessary, and IIRC, may have even found it faster around the track without it (citation needed). It was the autocross junkies screaming for a LSD that caused them to release a diff option later in the model run.

This is not a burnout car and besides, in a light, well-balanced car, you can light up both wheels. As an example, it's fiendishly difficult to determine if a used Miata has a limited slip diff or not. Many things have been tried, the most conclusive (short of opening the diff carrier), is to call Mazda with the VIN. (sorry for all the Miata references, it is my area of "expertise").

This car will have a lot more power, sure, and I am guessing that I will eventually get a Torsen for my 818. But I expect to have plenty of fun with the open diff first. I doubt many people will notice the open diff (barring the autocross crowd and folks who frequent tight, technical tracks).

[BrandonDrums]

I do recall a top-gear episode where they test the Porsche Boxter S which didn't have a limited-slip diff. Stiggy said it slowed the car down so it would benefit from an LSD.

In my WRX, I routinely get the inner front wheel to spin when I'm exiting a tight turn and that's with AWD. I don't think an LSD will be that important in a straight line but when you start pushing solid torque numbers, the torque will look for places to go so I'm sure some 1 wheel burnouts will take place without an LSD unfortunately.

For me though, I'm doing just an OBX cheapo LSD...http://www.rsaperformance.com/obxjdmhefrls.html

I've done quite a bit of research and they work out well for those who have used it.

[16g-95gsx]

I was thinking the same thing, stock 5spd trans with OBX LSD front diff would likely handle the power necessary. Has anyone bothered to treat the gearset in order to perhaps gain a bit of strength from them without upgrading them entirely? The 5spd trans can be had for dirt cheap, so it seems like it might be worth holding onto it, and trying to get the most out of it before upgrading to something as pricey as the PPG gearset. While that might be worthwhile on a full weight, high powered Subaru, the 2wd lightweight/lower powered platform probably wouldn't need something quite that beefy. The OBX front diff is all of 360 bucks on ebay brand new, and from what I've been told the unit is pretty stout for the money. This is all what Ive been told, not my personal experience, but it seems like it would be worth trying before spending the money on a 6psd or PPG gearset for such a modest HP car.

[bu11dogg2]

Some have swapped in a Legacy GT (turbo model 05-09) gear set. The gearing is different and some say it's more stout.

The typical swap includes 1-4 with the stock wrx 5th.

[crobin4]

Some have swapped in a Legacy GT (turbo model 05-09) gear set. The gearing is different and some say it's more stout.

The typical swap includes 1-4 with the stock wrx 5th.

That is the word. I can't remember the ratios right off the top of my head. I do remember second gear is longer. 1.82-1 or 1.84-1 (I think) as opposed to 1.94-1 in the WRX box.

[emironov]

Another Subaru owner here chiming in. I'm very interested in this kit, but I would have great reserves about the WRX transmission, even at lower power levels. Unless you are going to rebuild the transmission, including new gears, from the beginning, you will have a good chance of running into issues. Furthermore the WRX axles are something I would stay away from. Remember this will be a used transmission that when through who knows what before it got to you. The 818 will be a car meant for flogging, and you don't want the tranny going out on you while doing it. While I think the 5 speed should be an option, I don't think it should be the ONLY option.

I'm also slightly bias. I am sitting on a 2005 STi race car that I've been very passively trying to sell. If the STi can be used as a donor, including transmission, I will be absolutely in for this kit. However I am not going to be up for getting more parts just because not all of the STi's will work.


Ugly car, but boy is she fast!
http://forums.nasioc.com/forums/showthread.php?t=1812281

[armstrom]

For those who really want to use the 6mt tranny you may want to check this out:
http://www.possumbourne.co.nz/images/products/Center-Diff-locking-tube1.jpg
Here's a link to the product page.
http://www.possumbourne.co.nz/trans_diff_parts.html

I can't take credit for finding this... Markat from the exocars forum found it. He's having a car built with with an STi engine and has been searching for a way to keep the 6MT. The price is said to be around $400 USD but you need to contact the company to get an exact quote.
-Matt

[16g-95gsx]

Does anyone know how the transmission is controlled in similar applications where it is placed behind the driver vs the way it normally is located in Subaru's? Obviously the specifics of the 818 aren't finalized but this isn't the first time this powertrain has been used in a rwd application. Just curious

[PhyrraM]

Does anyone know how the transmission is controlled in similar applications where it is placed behind the driver vs the way it normally is located in Subaru's? Obviously the specifics of the 818 aren't finalized but this isn't the first time this powertrain has been used in a rwd application. Just curious

In 5-speed models there is no 'control'. It's competely passive. The trans output is split equally front-to-rear by a differential. Any slip on one end is compensated for by a viscous coupling in the center differential.

Bypassing the center differential and 'locking' front to rear makes everything locked up and rigid.

Once it's all locked up, the unneed output can be diconnected and the remaining one still spins.

[thebeerbaron]

I think 16G is asking about the cables that actuate the manual transmission. I saw a video of this at some point, but I'll have to dig for it. I think it might have been someone demonstrating how the transmission shifted after installing the FWD conversion bit. Or maybe it was the video that showed how the crazy shaft-within-a-shaft transmission worked. Let me get back to you on that, if I find it I'll post it here.

Synopsis (from my dusty brain), there are cables (or is it one cable?), which will likely be custom, that attach somewhere towards the rear of the transmission. Cable routing is one of those things that is going to give Jim the eye twitches again.

[PhyrraM]

Ah, I see.

I've seen both cable and rod based conversions.

I would Google to see what they do on mid-engined sandrails that use Porsche and VW gearboxes. The procedure will be almost exactly the same.

[16g-95gsx]

Yep, I'm curious how it physically is shifted. An auto trans would be simple, but a manual makes me wonder. I'm sure I could search for it online, but I figured one of you guys may already know.

[thebeerbaron]

As I recall, there's a single "doohickey" that does the gear selection. It's a rod with something akin to a universal joint on the end. It has four motions - in, out, twist left, twist right. I looked for that video a bunch last night, didn't find it. Sorry I can't be more specific, I'll keep looking.

[readymix]

Saker did this with their SV1/SVS kits using the Subaru engine parts. There is minor modification to the stock 5 speed that requires the center differential section to be removed (it's a module, it unbolts and pulls off IIRC) and a blocking plate covers the hole. There is a local on our Minnesota forums building an Exo car with a Subaru engine/drivetrain that got a Saker blockoff for his setup.
The people talking about AWD vs 2WD and transmission strength are pretty much correct. The "glass transmission" problems with the WRX 5 speed are due to the transmission design for the 02-early04 WRX models. The design was an older design that was used for N/A applications. They bolted a turbocharged power plant up to it, and it just couldn't handle launching. But that is a problem related to wheel spin, as was mentioned. Since there's no breakaway torque spin on launch, all the stress is absorbed by the driveline parts. 1st and 2nd gear love to chew teeth on these things. In a 2WD config, you'll spin tire, and that releases the strain on the parts. There are plenty of 300whp or so WRXs flying around the Twin Cities area on stock transmissions without issue.
6500 for upgraded gears? Man, the price has gone up considerably. I paid 3150 for my PPG straight cut WRX 1-4 gearset a few years ago, toss in a new set of synchros and it totaled out to around 3400 for the whole deal. Granted, I know all the local techs as close friends, so getting a tech involved in the labor portion for the cost of beer or pizza was helpful. But I don't think that'll be necessary for most folks. IMO, 300whp on the stock transmission should be fairly reliable, and 300whp out of that motor in an 1800lb car will be absolutely out of control fast.

[PhyrraM]

... The "glass transmission" problems with the WRX 5 speed are due to the transmission design for the 02-early04 WRX models. The design was an older design that was used for N/A applications. They bolted a turbocharged power plant up to it, and it just couldn't handle launching.

Umm. Subaru has had turbos on EJ motors since the day they were introduced in '89. There was nothing new or converted about the transmission when the WRX was introduced to the USA in '02. We just finally had a turbo model, so we finally got a turbo transmission too. The rest of the world had them the whole time. In fact, the USA already had the same basic transmission behind a turbo 2.2 in the '91-'94 Legacy SS model.

There has been a steady stream of upgrades to the same basic transmission design since it was a 4-speed in the mid '70s. An upgrade path that continues to this day.

[readymix]

Umm. Subaru has had turbos on EJ motors since the day they were introduced in '89. There was nothing new or converted about the transmission when the WRX was introduced to the USA in '02. We just finally had a turbo model, so we finally got a turbo transmission too. The rest of the world had them the whole time. In fact, the USA already had the same basic transmission behind a turbo 2.2 in the '91-'94 Legacy SS model.

There has been a steady stream of upgrades to the same basic transmission design since it was a 4-speed in the mid '70s. An upgrade path that continues to this day.

I was given misinformation I guess. The local techs usually know their stuff. And maybe I'm misquoting on that. But yes, I agree, the transmisssion overall basic design has been the same for decades. I'll admit, I've only been in the Subaru world since 2003, so as far as exacting accounts on the history of the car goes, I'm not all that well versed.
I believe any late 2004 WRX had the new "RA width" gears. You can usually tell because it was the same time they changed the drain plug from a hex shape to a T70 Torx bit. There was a problem with 10 minute oil change lackys mistaking it for the oil drain plug, draining the tranny, then overfilling the oil.

[readymix]

OH, crap, just re-read your post again to make sure I soaked it all in. Please don't assume I'm one of those kids that thinks turbo subarus didn't exist till 2002. :\ My technical knowledge of them starts then, but the awareness of different models and such goes back to the early 90's/late 80's.
It's funny, because it's that kind of "it didn't exist till I saw it" attitude that made Nasioc suck for a while, and why I still don't go back. Don't want to give the impression that i'm in that boat.

[PhyrraM]

Nope, not at all. I just like to clarify when I can.

Simply stating that the US WRX had the most current upgrades for the time minus the RA gears, likely because 227 HP was well under what Japanese market cars had - and not even all of them had RA gears.

[VF48WRX]

I just wanted to chime in as a Subaru enthusiast, builder and future 818 customer.

a stock subaru EJ205 would be quite acceptable for this chassis. Power to weight is everything. A few years ago I did some modifications and tuning on a Porsche 356 Speedster replica with a Subaru powertrain, and we ended up with 250whp (stock was 150whp) and the car was scary. I felt it was too much power for that particular kit car's brakes, suspension and chassis.

I personally would be happy with 250-300whp and that can be had with a stock motor with a turbo upgrade.

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[vader wagon]

IMHO, the 5-speed tranny's bad rep came from guys thinking they bought a "rally car" and absolutely abusing them. The 02s were *weaker* than the 03+, but I don't think that's a huge difference as it's the loose nut behind the wheel that breaks WRXs and STis. Example, I've got an 03 WRX that I have not babied for 125+K and I've got no issues with my stock drivetrain--everything is still stock aside from simple bolt ons.

Regarding the 818, I think a "stage 2" WRX doner would be relatively cheap and would be about 285-hp at the crank. This with a light car? It'd scoot. IMHO, outside of a track, it'd put down more than enough power to get you jailed everyday of the week. I'm running a "stage 2" set-up in my wagon and I'm limited by the law and the slowpoke in front of me, not the car itself. Case in point, I catch up to sports cars (Porsches and Corvettes) and sport bikes crossing Highway 2 or 20 in Washington state all the time. Power and handling aren't lacking even at being "only" stage 2 in a "wimpy" 2.0l WRX wagon.

Lastly, let me suggest this forum: http://forum.subiefanatic.com/. SubieFanatic is a small forum with about 50-active members. However, it's got a solid knowledge base and a member group that does not approve of anti-newb responses. NASIOC is a great technical resources for Subies, but their membership can be a little harsh to those that are new to the Subie world. Anyway, check out SF if you're interested in learning more about Subies and the community. BTW... I think that the 818 will be a huge crossover hit and I can't wait to see it!

[Scubynubie]

First time poster, and Subaru owner. I am totally geeked up for this kit, as it may be just what I'll need in a couple of years when my WRX gets a bit tired. Some good information in this thread, but I wanted to chime in. I actually work for a company that specializes in Subaru performance, and we actually do a fair amount of gear sets/transmissions.

First, here is a good link with some comparisons of the WRX Gear Sets:

http://flatironsrally.typepad.com/faq/2010/05/comparison-of-subaru-gear-sets-wrx-legacy-gt-sti-ra-and-more.html

The WRX transmission does get something of a bad rap, and the reasons for this have been covered above. I'll just say that the main reason for gear failures come down to: how the car was driven, the type of clutch used, and type of fluid. Basically, AWD cars don't like to be launched typically, and the WRX exemplifies that.

Because of the weight reduction in this kit, I really don't think that the gears in the 5MT are going to be the issue when it comes to strength. However, if I had to guess, I'd say that the weak link will be the front ring and pinion, or possibly the axles. Even though the car is much lighter, I would assume that you are going to be able to put much wider tires on it than you can with the WRX. So if you have a lot of grip, and all the power is going through one diff, that can be a problem.

As far as the Subaru 5MT, here are some pointers for picking one:

First, all WRX 5MT's have open differentials, even to this day, so if you want to put in a TBD, or LSD, you'll have to look to the aftermarket for that. OBX makes a TBD, but I personally wouldn't use it as a paperweight. Modena also makes a motorsports TBD, and even though it is a bit expensive, it is a fantastic diff. Cusco makes a clutch type LSD for the front, and you can pick between a 1, 1.5, or 2 way diff. They are a bit difficult to come by at this time though. I believe that OS Geiken makes an LSD for the 5MT as well.

The STI 6MT does have a front TBD in all years. If memory serves, they are all mechanical TBD's, but they may have switched over to an LSD at some point up front.

Also, the 5MT and 6MT are completely different animals, and you can not change any parts over from one to the other.

However, the JDM STI from version 6 and older used a 5MT, and most parts from the version 5 and 6 (1998 - 2001)can be retrofitted into the USDM 5mt with a bit of work. If you go older than the version 5, the case changed to the point where you can not use those parts any longer, but if you can source a complete transmission, they will bolt on similarly.

In choosing a 5MT, you ideally want one from a 2003+ WRX, as explained in the link above. But the final drive did change a bit too.

From 2002 - 2005, the WRX had a 3.9:1 final drive. In 2006 - 2007, Subaru switched to a 3.7:1 final drive, but then in 2008, they went back to the 3.9:1 final drive. Because of the light weight of the kit, that taller final drive may be the most desirable.

As far as ratios go, here are the WRX gear ratios from 2002 - 2007:

USDM WRX
1st - 3.454
2nd - 1.947
3rd - 1.366
4th - 0.972
5th - 0.738

The two most common gear swaps into the 5MT case are the:

Legacy GT/STI V.6 gears

1st-3.166
2nd-1.882
3rd-1.296
4th-0.972
5th-0.738

And the STI RA Gears

1st - 3.083
2nd - 2.062
3rd - 1.545
4th - 1.151
5th - 0.825

For comparison, here are the ratios for the 2006+ STI 6MT:

1st - 3.636
2nd - 2.235
3rd - 1.521
4th - 1.137
5th - 0.971
6th - 0.756

The thing to not with the 6MT is that you don't have a taller 6th compared to 5th, it really is just a close ratio set utilizing an extra gear.

Here is a very good link to a gear comparison chart with speed compared to rpm:

http://www.rallispec.com/Subaru%20Gear%20Chart.htm

[Ks2]

wow alot of trash talk on the 5 speed. i have a JDM sti motor, modified making over/around 350 hp and a stock 5 speed that came in my 02 it has seen track days, runs down the drag strip and has gotten me more kills at stoplights around town then i can count. the transmission is not nearly as bad as some are painting it to be and i prefer it to the 6 speed for daily driving and track use.

the transmission is not bullet proof by any means but a tablespoon of common sense will make it last a long time (a good clutch and smaller tires/rims will do you wonders as well).

EDIT on a completely unrelated note, just noticed that it seems there is more activity in the 818 forum (for a car that doesn't even exist yet) then on all but one of the other forums here...

[Kay95]

The newer suby trannies arent that much better than the older ones. People routinely break Lgt, Fxt and Ra boxes. Just ask andrewtech that does alot of builds. So get a cheap one and have a backup.


The best to get would be the Forester XT tranny. Its the same as a WRX but with 4.44 final ratio.


You can get strengthened ring and pinion gears through subaru as group n parts. You will pay the price because they are expensive.

The OBX has had alot of success. Though out of the box they are crap. You must take them apart then clean and deburr everything. Do that and you wont run into problems.

[16g-95gsx]

Can anyone verify the weight of the 6spd? I've heard all sorts of numbers. The 5spd seems like it will weigh in around 100lbs inthe configuration that we'd want.

[VF48WRX]

The last one I shipped was 300lbs with some accessories on the same skid.. so maybe 250-300. It's a heavy mofo for sure

[16g-95gsx]

That's absurdly heavy for a 4 cylinder transmission. Can anyone confirm?

If it cost 150lbs worth of weight on the car I would far rather run a PPG'd 5spd than a 6spd on this car.

[BrandonDrums]

That's absurdly heavy for a 4 cylinder transmission. Can anyone confirm?

If it cost 150lbs worth of weight on the car I would far rather run a PPG'd 5spd than a 6spd on this car.

What he said. Plus, 6 speeds are really expensive and have really short gear ratios. You pay for the active center diff that you then weld shut.

Get the 5 speed, I know it will hold in 2wd config but if you really want stronger gears do the PPG.

[16g-95gsx]

Right, the price isn't a concern for me, not that I'm baller, but I enjoy having a truly reliable setup. However, if it gains 100lbs on the car then I think it's ignorant to choose a 6spd. I agree that the 6spd is just a tight ratio'd 5spd. I agree that in a stock application the 5spd may work, but with stickier racing tires and higher powered outputs I think you will likely still see failures.

[BrandonDrums]

Right, the price isn't a concern for me, not that I'm baller, but I enjoy having a truly reliable setup. However, if it gains 100lbs on the car then I think it's ignorant to choose a 6spd. I agree that the 6spd is just a tight ratio'd 5spd. I agree that in a stock application the 5spd may work, but with stickier racing tires and higher powered outputs I think you will likely still see failures.

Yes, quite possible indeed. Drive responsibly and invest in gears if you really want to push it.

[Scubynubie]

Okay, shipping weight on a complete MT is 145 lbs. Figure about 25 - 30 lbs packing.

Shipping weight on the 6MT is 250 lbs. Those are packaged a bit more, so I'd say about 50 lbs packaging give or take.

The 6MT is definitely heavier FWIW...

Also, since you are going to have to remote mount the shifting mechanism, the reverse lock out and different gates on the 6MT might be an issue too.

[riptide motorsport]

seems to me the obx front diff with the five speed should be more than sufficiant for the job, and be cost effective..........Steven

[Scubynubie]

seems to me the obx front diff with the five speed should be more than sufficiant for the job, and be cost effective..........Steven

You have to remember that all the power is going to be going through the front diff. I personally wouldn't trust a poor quality knockoff for that, but to each their own.

Also, FWIW, a front diff install, or gear install on the 5MT is something that you will want professionally done. And even then, you really need someone that knows Subaru transmissions. They are a lot harder to get right than you would think, and I have seem so many transmissions destroyed from shoddy installation....

[Gollum]

I've pulled the 6 speed from a car, and even with a lift and a good tranny jack it was a serious job. They're really heavy.

Regarding the power for the "V8 guys" (which I kind of am), 400hp pushing a 1800 pound car is in the ballpark of the veyron.... The limitations at these levels will be set by how much tire we can run, how much downforce we can get, and how aerodynamic the body is.

[Mechazawa]

A lot of folks are having good luck with the OBX units in FWD and RWD applications, so i would not worry about it, I think someone wrote something like "that's really heavy for a 4 cylinder transmission" you have to think of it as a 300 hp transmission, and one with a super complicated transfer case and 6 forward gears at that.

I think I will be quite happy with the normal WRX 5 speed, 6 speed transmissions are most useful on engines with very narrow usable bower bands (the kind Honda used to make), Subaru does not build that type of engine. I think more than say 300 hp is a little silly in this sort of car, and the WRX transmission will handle that just fine.

[16g-95gsx]

300bhp is NOT that much power, so I still feel that 200lbs for the transmission is absurdly heavy. I agree that the DCCD is apt to add a ton of weight, but even then it seems that the 5spd is far better for this application.

[Ks2]

the big difference between the 5-6 speed for me, and in my opinion, is freeway cruising i like the 5 speed but in my WRX i sit at 3k-3500 rpm, on boost basically on the freeway... passing is so much fun it should be (and actually is) illegal but fuel economy is piss poor. In my buddies 6 speed swap however, passing just means shifting down to 5th and flying around someone then going back up to 6th and cruising along at 2-2500 RPM. i played with the DCCD but i cant see myself changing settings on it constantly and in a car like this i don't see myself driving more then an hour to any one particular place so a freeway cruising gear is unnecessary (for me at least) i would rather have less weight, less complexity and is overall a cheaper and easier to source transmission.

as for the veyron territory all i can think of the little caterham on top gear going round their track faster then a veyron. the 818 will have similar weight and displacement (those have a 2.0l duratec in front engine rear wheel drive) imagine what a mid engine turbo version would do? http://www.caterham.co.uk/ the most powerful super 7 they have is 260hp cosworth

[PhyrraM]

Random thoughts on recent posts:

WRX 5th gear: .73
STI 6th gear: .75
This means that cruise RPMs are slightly higher with the 6 speed.

The fuel mileage is not from the gears or the RPMs. It's from the fact that Subaru has the 2.0 turbos pig rich in the factory tune.

5 speed 1st gear: 3.16
6 speed 1st gear: 3.63.
In a car as light as the 818, first gear on the 6 speed will be almost unusably short.

A properly designed rear suspension geometry will put very little differential load between the rear tires, hence less need for a LSD. As long as the parts that take engine torque (ring and pinion, bearings, and carrier) are up to the task, the function of the actual limited slip mechanism will see very little load (short of one tire on a very low friction surface and the other on the road with large throttle application). OBX will be fine if FFR does their suspension homework.

The Veyron is not a racetrack car. It's not even a 'spirited cruise up the mountain' car. It cannot be compared to the 818 on any level except for acceleration.

DCCD is a function for controlling a variable front-to-rear torque output and will be functionally removed with a 2WD conversion. It will likely be physically removed also.

[16g-95gsx]

I guess I should add in that my comment was that the DCCD adds weight to a stock 6spd and therefore a large chunk of the weight difference in 5spd and 6spd comes from that. I fully understand that if the 6spd were able to be used in this car that the DCCD would be removed but rereading what I said it sounds as though I didn't realize that.

I still feel a 5spd is the way to go. I'm not sure if case flexing will be an issue in this car with this type of configuration. I also feel that the gearsets can be treated for a bit more strength. In the end a PPG gearset would add very little weight but certainly get the job done if other options failed.

I know many people will cringe, but how are the Subaru auto transmissions? In some cases when well set up there is some benefit to a solid auto trans.

[riptide motorsport]

I asked about the auto, doesn't look good :(

http://thefactoryfiveforum.com/showthread.php?1064-standard-or-auto

[PhyrraM]

DCCD adds very little weight. In fact DCCD was available on STI 5-speeds before the 6 speed was introduced. STIs never came to North America until they had 6-speeds, so the 5 speed w/DCCD version is not commonly discussed.

DCCD is just a clutch pack in the center differential that is controlled by a duty cycle solenoid. I'd be surprised if the DCCD hardware added more than 10 pounds to the transmission.

The 6 speed is magnitudes heavier than the 5 speed because it has stronger gears, has a positive pressure oiling system, has extra cogs, larger ring and pinion, etc. The WRX/STI had grown from 2600 pounds in 1993 to 2400 pounds by 2001. The power had gone from 240ish HP to 300+ in the same years. Subaru had not had an all new manual transmission since the 1970s. Knowing nothing of the current efficiency push, I'm sure the 6 speed was designed for a 20-30 year "in production" life span. Those are the reasons it weighs as much as it does.

IIRC, the older Japanese market 1993-1997ish WRX 5 speeds had longer first gears. Those might be a good one to source for gears and use the North American market 3.9 final drive into.

Torque to the gears will be the same for the 818 as it would be in a WRX with equal power. The time that torque is applied will be less because acceleration is faster due to the light weight. If case flexing failure is related to the amount of time the case is under duress, then the case can be considered more durable in the 818 as it will see about 2/3 of the 'loaded' time per gear. If the case simply 'pops' on a momentary overload, then not much will change.

[Ks2]

good thing i added 'in my opinion' haha, i have always been under the impression it was the gearing in the transmission and not so much the motor causing the higher RPM in my WRX versus my friends, interesting point on it though given the fact that both of our cars are extensively modified that might explain some part of that as well since both are tuned differently

[StatGSR]

I asked about the auto, doesn't look good :(

http://thefactoryfiveforum.com/showthread.php?1064-standard-or-auto

That thread is full of a lot of misleading info. basically, if a 6 speed will fit, an auto will physically fit as well. Subaru made FWD autos (and manuals) until 96-97? that will bolt strait up to any EJ/EG/EZ after that the company removed all FWD models from the line up. In stock form Subaru's autos are not that great, but with a little work they can be extremely fast and shift pretty nicely(the fastest subarus all use a built auto trans, granted those autos will cost as much as if not more than a PPG 5spd). granted the shift logic for anything but strait line acceleration will most likely be horrible.

[16g-95gsx]

What us physically wrong with Subaru autos? I'm curious what their failure modes tend to be.

While Im not sure if an auto is the way to go there ARE a huge amount of benefits that can be had from a very fast accelerating car with an auto. No missed shifts, constantly in boost during WOT, less strain on divetrain parts during launches and shifts, and huge torque multiplication and launch benefits from a stop. A high line pressured auto trans can have tremendously faster shifts than a standard manual, and they nail the shift correctly everytime vs potentially missing the shift in a manual or worse yet hitting a lower gear accidentally. With a very torquey turbo setup you can run a tighter converter setup making it decently efficient with great street manners. The auto will weigh more than a 5spd Im sure, but probably far less than the pig of a 6spd and being a typically less desired trans it can probably be picked up cheaply. I agree that if it physically fits then there is a way to make it work.

Then for people like myself who play around, there is also the potential to have a paddle shift setup if you want to still have manual control.

[Gollum]

The Veyron is not a racetrack car. It's not even a 'spirited cruise up the mountain' car. It cannot be compared to the 818 on any level except for acceleration.


I understand you point, but I think you missed mine. mn_vette seems to be under the impression that he'll miss having a big monster V8 and doesn't seem to be able to call the 818 a "true sports car". So I swung the opposite direction comparing power to weight ratios of the Veyron, with it's 1000hp. But if we'd like some direct V8 comparisons...

2010 Corvette ZO6
Weight - 3175
HP - 505
LB Per HP - 6.28

2010 ****** GT500
Weight - 3924
HP - 540
LB Per HP - 7.26

2010 Dodge Viper SRT-10 Coupe
Weight - 3454
HP - 600
LB Per HP - 5.75

Hey, Let's even go exotic. Well into the 6 figure range the
2004 Saleen S7
Weight - 2750
HP - 550
LB Per HP - 5.00

So even if you spend an extra 20k building a PPG 5 speed and a monstrous 2.5L motor that can hold 400+ hp without breaking a sweat, I think you'll still be looking good compared to the price of ANY of those vehicles above, and have a HECK of a lot more power to weight. Even if you were to have a shop BUILD your 818 FOR YOU I bet you could still come out cheaper than some of the cars listed.

That my friends, is one dang "sporty" car. It's going to have (potential for) straight line acceleration almost incomparable to production vehicles, and it's going to corner as good, if not better than the featherweight Lotus vehicles. It's going to be one crazy package.

[mn_vette]

I understand you point, but I think you missed mine. mn_vette seems to be under the impression that he'll miss having a big monster V8 and doesn't seem to be able to call the 818 a "true sports car". So I swung the opposite direction comparing power to weight ratios of the Veyron, with it's 1000hp. But if we'd like some direct V8 comparisons...


Now you are trying to put words in my mouth.

I have no issues giving up a V8 as long as the car has enough power to beat a typical V8 car. There is a replacment for displacement, its called boost. Now that I think about it, the quickest vehicle I've ever ridden in was a pickup truck with an inline 6 in it.

The estimates on the opening post of this thread show how quick this car will be depending on how people want to build it. We'll have to see how things turn out. The one big unknown for me is how the short first gear in the transmission will be off the line and then the low rpm starting off in second. I'm sure FFR has some good ideas with the chassis that they have, I'm hoping they will give us a bit more info sometime soon.

[Gollum]

Being a V8 guy that seems like an ok daily driver horsepower number to me rather than a real sports car.

I didn't mean to put words in your mouth. I guess I just happened to read the above statement and didn't really see you give much sign that you thought otherwise after giving your own 1/4 mile estimates.

I mean, I HAVE met guys that think real cars START at the 10 second mark, and own and drive 800+whp vehicles. So your first statement, even after the rest of your first post, could have stood as your opinion.

And even if you're one who can deal with not having a huge V8, there will be others that can't. I understand where they're coming from. I don't agree with them myself. But their thoughts have their own merit.

As to replacement for displacement, you're correct in the way that you mean. The way in which I prefer to think about it is "there's other avenues for power and speed than displacement". In the end, I truly believe there's no "replacement for displacement" because "all things being equal" more displacement makes more power. Every time. The case in which this isn't the case, is when all thing's AREN'T equal. I think Ford's new Coyote engine kind of proves this, as it's already shown to make over 100hp per liter under 7000rpm. With higher RPM cams and valvetrain it could easily match the 120hp per liter of the 2.0L Honda S2000 motor. All it takes is the right design to match and the power is there.

I think we can all agree though, boost is fun on just about any engine!

[mn_vette]

I didn't mean to put words in your mouth. I guess I just happened to read the above statement and didn't really see you give much sign that you thought otherwise after giving your own 1/4 mile estimates.


Ok, I see what you are saying. I guess what I ment to say is that when I hear 227 horsepower my first thought is not of a fast sports car, especially with mustangs putting out almost double that amount. I tried to put up the quarter mile time estimates to show that this will be a pretty fast car with the base horsepower and gets faster as you increase it.

And I agree, boost is fun on any engine.........until it goes pop, so be careful with the mods.

[PhyrraM]

The Subaru autos have ATF temperature issues. I do not know what fails in the transmission physically, but whatever it is - it's induced by fried ATF.

FYI, the 4 speed autos are the same basic design as many other Japanese automatics during the same years. Nissan Pathfinders for one, but I'm sure the list is fairly long. Of course the case and transfer components are Subaru specific, but the planetaries, valvebody, etc. are a fairly common design.

I know nothing about the 5speed auto and CVT, so can't comment on those.

[PhyrraM]

I guess I'm in the minority when I think that Mustangs (and Camaros/Challangers) are not sports cars?

The only American car I would call a sports car is the Vette. All the rest I would call muscle cars, because the emphasis is clearly on acceleration and style.

When I think of sports cars, which the 818 should be for me, I think of the old MGs and Triumphs. I think of the Miata and S2000. I even think of the CRX Si and Fiat X1/9. I think of cars that have nerve-ending-like feedback and reaction to input. I think of cars that do alot with what little they were given. I think of cars that put a smile on your face because of how they make you feel, not how they make others look at you.

I think that anyone looking purely at acceleration numbers of the 818 might be missing the point and won't be happy for long. I'm thinking they might need to step up to the GTM now, rather than later.

Just my opinion, of course. Sorry for the off-topic.

[16g-95gsx]

The Subaru autos have ATF temperature issues. I do not know what fails in the transmission physically, but whatever it is - it's induced by fried ATF.

FYI, the 4 speed autos are the same basic design as many other Japanese automatics during the same years. Nissan Pathfinders for one, but I'm sure the list is fairly long. Of course the case and transfer components are Subaru specific, but the planetaries, valvebody, etc. are a fairly common design.

I know nothing about the 5speed auto and CVT, so can't comment on those.

That's what I was expecting. Automatic transmissions (and any performance transmission really) is heavily influenced by heat. Torque converters in high performance applications dispel and ENORMOUS amount of heat, and can boil fluid within a matter of seconds. The second the fluid is heated, the cooling properties and lubrications properties are impacted and destruction quickly takes place. This luckily is easily remedied by properly choosing a higher temp capable racing trans fluid, larger trans fluid cooler (ideally with a fan to reduce heat during static conditions for those that like to stall the trans up at a stop), and properly selecting the slip or stall of the torque converter. I should look more into the 4EAT specifically and see where it's weak points are. Id imagine with the very torquey turbo setups that a car like this would be apt to run (Evo 3 16g, HTA68, etc) that a very tight converter could be ran with very little issue and still be tremendously potent at the track (in all forms of track racing).

I'm definately in the boat where I would like this car to be a 10 second capable car while still competing elsewhere. In all honesty I don't consider an 11 second car all that special, there are far too many stock-ish setup cars out there that will run that without much effort. I think with the weight and powerplant potential that this car would be capable of, you start with a fantastic "blank slate" that makes someone with a little ingenuity and effort capable of absolutely tremendous things.

[BrandonDrums]

I guess I'm in the minority when I think that Mustangs (and Camaros/Challangers) are not sports cars?

The only American car I would call a sports car is the Vette. All the rest I would call muscle cars, because the emphasis is clearly on acceleration and style.

When I think of sports cars, which the 818 should be for me, I think of the old MGs and Triumphs. I think of the Miata and S2000. I even think of the CRX Si and Fiat X1/9. I think of cars that have nerve-ending-like feedback and reaction to input. I think of cars that do alot with what little they were given. I think of cars that put a smile on your face because of how they make you feel, not how they make others look at you.

I think that anyone looking purely at acceleration numbers of the 818 might be missing the point and won't be happy for long. I'm thinking they might need to step up to the GTM now, rather than later.

Just my opinion, of course. Sorry for the off-topic.




No apologies needed. You hit the nail on the head...but I do want the 818 to turn heads as much as corners.

[Scubynubie]

No apologies needed. You hit the nail on the head...but I do want the 818 to turn heads as much as corners.

This is the key. This car is going to be fast in a straight line even with a stock 227 whp. I'm at 5280 ft. elevation, and they dyno at about 165 whp stock. But by making the car 2WD is going to reduce drivetrain losses, and the weight is going to make acceleration awesome. And if this car can find grip, it is going to be super fun, and super fast.

IMO, the stock 5MT is reliable up to about 280 whp. If know how to drive it, the 5mt can hold more power than that, but i you want the stock trans to be reliable, then I'd say that 300 whp is a good place to shoot for. And in an 1800 lb package, that 300 whp will be awesome.

300 whp is tough to hit with the 2.0 liter though. Something that might be worth considering would be to build a 2.0 with the late WRX crank, which is cross-drilled for improved oiling. The JDM 2.0 STI engine (not availble in the US, is a semi-closed deck EJ207 with big valve cylinder heads) revs to 8,000, which is about 500 rpm higher than the USDM model. In this car, building a 2.0 that revs higher could be really interesting because it will put less stress on the transmission (making less torque) and will make the relatively short gearing work to your advantage.

[Ks2]

The JDM 2.0 STI engine (not available in the US, is a semi-closed deck EJ207 with big valve cylinder heads) revs to 8,000, which is about 500 rpm higher than the USDM model. In this car, building a 2.0 that revs higher could be really interesting because it will put less stress on the transmission (making less torque) and will make the relatively short gearing work to your advantage.

this is what i currently run in my WRX with the stock 5speed and i absolutely love it 300hp is very do-able with the 5speed with this motor, the version 7 you mention has AVCS and OCV valves i think iaperformance still sells the wiring conversion kit which adds some wires and repins the stock US wiring harness to get rid of the TGV's and make the AVCS and OCV valves work. the ej207 CAN be found in the US but are extremely rare nowadays, keep an eye on ebay for one that isnt horrible high mileage though these motors are really tough

of course for a cheap build you can get the 2.0l heads and put them on a 2.5l shortblock for a bump in compression displacement and bottom end power this is what i am currently building for the 818 out of the blown 2.0l i swapped for the STI one

http://cgi.ebay.com/ebaymotors/SUBARU-WRX-STI-VER-8-COMPLETE-6SPD-SWAP-JDM-EJ207-STI-/270743361326?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f098fd72e

there is a version 8 with 6 speed

[BrandonDrums]

300 whp isn't that difficult to hit on a 2.0. An HTA68 or 18G-xt would be a cost-effective way to get those numbers.

300 is about all you'd want to do though, above that and the fun-factor starts to decrease unless you start pumping real cash in to the engine and turbo/wastegate etc.

On a 2.5 though...330whp is easy.