Gearing selection Question

How does one going about choosing a gearset / gearing?

In an Ideal world, do I want the exact same RPM Drop in every shift? or do i want less drop in the higher gears ?

Do I want the rpm drop to exactly match my power band? (i would think this is a Yes, but i'm guessing)

if my power band is 2,000 rpms, do i want exactly a 2,000 rpm drop every shift?


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That's what i really want to know.. and just to share and post more info and risk explaining too much:

I've recently scored an Outback impreza transmission for my rally car!

I'm wondering if there will be value added by trying to play "mix N match" with some of the gears..

I was using : 3.545 / 2.111 / 1.448 / 1.088 / 0.780 / 4.111FD

and i will be switching over to :

3.454 / 2.062 / 1.448 / 1.088 / 0.871

Rpm engagement if i shift at 7,000

2nd 4200 (2800 drop)
3rd 4900 (2100 drop)
4th 5250 (1750 drop)
5th 5600 (1400 drop)


.. and here's a list of other 5 speeds that i could potentially grabs gears from.

3.454 / 1.947 / 1.366 / 0.972 / 0.738 / 3.900FD - '02-'05 USDM WRX; 3.545FD rear diff
3.454 / 1.947 / 1.366 / 0.972 / 0.738 / 3.700FD - '06-'07 USDM WRX
3.166 / 1.882 / 1.296 / 0.972 / 0.738 / 3.900FD - '08-current USDM WRX
3.454 / 1.947 / 1.366 / 0.972 / 0.738 / 4.444FD - '04-'08 Forester 2.5XT
3.454 / 2.062 / 1.448 / 1.088 / 0.780 / 4.111FD - '04-current Forester non-turbo
3.166 / 1.882 / 1.296 / 0.972 / 0.738 / 4.111FD - '05-'06 USDM Legacy 2.5GT
3.166 / 1.882 / 1.296 / 0.972 / 0.738 / 3.900FD - '07-'09 USDM Legacy 2.5GT
3.166 / 1.882 / 1.296 / 0.972 / 0.738 / 4.444FD - '05-'09 USDM Outback 2.5XT
3.545 / 2.111 / 1.448 / 1.088 / 0.780 / 4.111FD - '98-'01 USDM Impreza 2.5RS
3.545 / 2.111 / 1.448 / 1.088 / 0.780 / 3.900FD - '96-'01 USDM Impreza L/OBS
3.545 / 2.111 / 1.448 / 1.088 / 0.780 / 4.111FD - '96-'99 USDM Legacy 2.5GT
3.545 / 2.111 / 1.448 / 1.088 / 0.871 / 4.111FD - '96-'99 USDM Legacy Outback
3.454 / 2.062 / 1.448 / 1.088 / 0.871 / 4.111FD - '00-'07 USDM Outback
3.454 / 2.062 / 1.448 / 1.088 / 0.825 / 4.111FD - '08-current USDM Outback
3.454 / 2.062 / 1.448 / 1.088 / 0.780 / 4.111FD - '02-'04 USDM Impreza 2.5RS/'05 Impreza 2.5RS Sport
3.545 / 1.947 / 1.366 / 0.972 / 0.780 / 4.111FD - '93-'94 USDM Impreza 1.8L
3.545 / 2.111 / 1.448 / 1.088 / 0.825 / 3.900FD - '95 USDM Impreza 1.8L


Also i included a Dyno of my last motor (Pick N pull RS 2.5 , with Delta 1500 cams , before and after Gorilla Intake)

The new motor so far is costing me $600 (big spender i know) my old STI block, new pistons with rings (little higher compression than a stock RS2.5) , and i traded a spare turbo motor for 05 RS heads + intake) i may also upgrade to the 3000 cams depending on exact cost, it will probably get a port and polish if I'm really nice to my crew chief who is super awesome.



So Realistically i'm wondering if i should try to chase down a used legacy or forrester XT transmission to grab their 1st, 2nd, and 3rd. , since that gearing is 3.166 / 1.882 / 1.296 / 0.972 ??

I've also got a 93 impreza FWD transmission sitting in my garage, and i know of a 95 transmission i could likely buy for $100 ... I'm not sure if either would be strong enough for the "massive" RS 2.5 power ... but .. just looking for input / advice.

also i would like to know what the Ideal setup would be.. even if its way out of my budget.. just cause you know, knowledge is power ...

Keep in mind you cannot just mix and match willy nilly. As a general rule later transmissions had wider gears. '02-'03 WRX transmissions had wider gears than '98-'01 2.5RS transmissions, for example and '04+ WRX transmissions had wider gears yet. Also, mid year '98 they changed the transmission case so earlier gearsets won't work in later cases or with later gearsets (to a point, the main change is they moved the position of the reverse idler gear a little bit, but everything related to that is affected.) And forget about using any FWD parts in an AWD transmission. They are far too weak and even then some parts don't interchange at all because the FWD trans has a solid mainshaft and the AWD has a hollow mainshaft so the pinion can go through to the center diff.

Depending on the year of transmission you got, it will be a 4.11 final drive, for an open light subaru, i would fins a 4.44 final drive set, they come in the auto tragics, so you just need a full rear diff, just grab the whole case, and then the ring and pininon from the front trans axel. it will essentially shorten all your gears. its an easier, and far less expensive option then trying to find a "perfect" gear set.. you will loose a bit of top end speed, but its not like you will ever hit 130+ in your open light any way. i top out at 115 with my 4.44s, cant remember the ratio on my 5th gear.

EDIT:
The Modena Group-N ratios are as follows:

1st gear: 2.917
2nd gear: 2.091
3rd gear: 1.555
4th gear: 1.176
5th gear: 0.900

(dont bust my balls on a having a modena dog box in an open light, i bought mine used with GEMS DCCD controler for 2K)


your other option, if you want to spend $$ on your car is to jump up the compression up to 11, or 12, then u wil just have more power across the whole rev range.

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I be sorry as a muthafucka I did, still sorry I did n' hustled ta peep what tha fuck I holla'd a lil' bit better, or at least try to.



Edited 2 time(s). Last edit at 07/26/2013 11:01AM by mke723.

Quote
mke723
Depending on the year of transmission you got, it will be a 4.11 final drive, for an open light subaru, i would fins a 4.44 final drive set, they come in the auto tragics, so you just need a full rear diff, just grab the whole case, and then the ring and pininon from the front trans axel. it will essentially shorten all your gears. its an easier, and far less expensive option then trying to find a "perfect" gear set.. you will loose a bit of top end speed, but its not like you will ever hit 130+ in your open light any way. i top out at 115 with my 4.44s, cant remember the ratio on my 5th gear.

EDIT:
The Modena Group-N ratios are as follows:

1st gear: 2.917
2nd gear: 2.091
3rd gear: 1.555
4th gear: 1.176
5th gear: 0.900

(dont bust my balls on a having a modena dog box in an open light, i bought mine used with GEMS DCCD controler for 2K)


your other option, if you want to spend $$ on your car is to jump up the compression up to 11, or 12, then u wil just have more power across the whole rev range.

Do both. More compression, and shorter gears.
And interestingly, many cars will pick up a bit of top speed because at higher speeds and MPG gearing, most car cannot pull max revs, they peter out somewhere..using the car I know best, the mighty Saab 96 with the great V4, they typical million miles I fist had would NEVER top 91-93 MPH with stock 4.88 final drive. Plopped in the ring and pinion from the giant killer 850cc 3 cylinder 2 stroke which is 5.43:1 and the car would do over 105mph--basically however high I dared rev the motor it would rev, even in 4th (.86)
Now the fantastic car that it is, it had a drag cd of like .32 which is clean so the all important aero resistance affected the car less than most horrible boxes. But that aero effect is a cube function thang, and that combined with MPG gearing is often the culprit..

Alex has some guys advising him on making a killer-diller motor and I am waaaaaaaaaaaaaaaaaaaaaaaaaaaaaay worried for him....I'm trying to get him to listen to reality: a 2500cc motor with even mid 11s comp is going to work real good with some 4.4 gears, not need to make it rad cause then the gearing drop in ALL those boxes will harm the yank in the car..even the "Group N" ratios are really just "pretty damn good in a motor that makes lotta torque", but not really close...(They're very close to my favorite Borg Warner T5 that I push for 2300 turbo Volvos and Xratties, except 5th---that fith is a real fifth to use, the T5 is so overdrive it is intended to use only on highway on transits OR to cruise longer distances to get away to places to PRACTICE---which is more important than some "way wicked rad--and peaky--motor)

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

with 4.44 and a usable 5th my top speed is still HP limited.

---

I be sorry as a muthafucka I did, still sorry I did n' hustled ta peep what tha fuck I holla'd a lil' bit better, or at least try to.

Quote
mke723
with 4.44 and a usable 5th my top speed is still HP limited.

sure, what compression? what cc engine?

the norm for 2.0 motors with tires round 64cm is 5.1:1 , 4,4 is really a ratio for tubo cars

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

the open class subarus i have worked on usually run the 3.90 gearing, the 4.11 and 4.44 are stock in the NA street cars, 3.90 in the newer ones, 3.54 in the wrx and sti.

my car is on my build page, 2.5l NA

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I be sorry as a muthafucka I did, still sorry I did n' hustled ta peep what tha fuck I holla'd a lil' bit better, or at least try to.

Worried about me? ya maybe i should be worried too..

and yep my crew chief has the short block done. old STI block + sti crank and rods ($100) and some sort of higher compression piston 12:1 i think ... ? with rings $500 ...

and i traded a spare motor for used heads and intake.. well one of my navigator buddies is looking for me...

If we were at 185 Crank HP before, i bet we pass 200 pretty easily .. but i'll be shocked if its more than 230 ... and yes i have 4.44 parts..

its more of a theory question then me dropping a bunch of money on custom gears... although my crew chief might have part of a 02 WRX transmission that may have a longer 1st gear... (the 2nd on it is toast)

no trick DCCD for my open light car.. although i would love one... but i'm (mostly) just trying to get it back on the road cheaply ... so far I've spent $600 .. I'll need to get some sorta ECU to run the motor ... hoping there's a cheap stand alone option for me (200-300) and we should hopefully be able to re-use my old 1500 grind delta cams.

seriously I don't know how much quicker the car will get. last time i rallied it the car was doing a 16 second 1/4 mile with a 10 second 0-60 ... Not exactly a barn burner...

more is always better right? although i have heard plenty of people preach doing small upgrades ...

Alex, one of my to do items right now is to source a .87 5th to swap in hopes of maybe getting some meaningful acceleration. We run the 4.44 final.

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-KTurner
Stomp down on the exhilarator and hold on to the wheel.

Keep in mind with the 4.44 you're going to want to have spare ring and pinions. The 4.44's are weaker than the other ratios because of the tooth size/count and break far more often. I have a stack of broken 4.44's in my shop. Even the fancy shot peened $750 Prodrive R&P didn't last any longer. We switched back to the 3.90 in Dave Hintz's car and never had another problem. Never broke a 3.90.

Are failures mostly on turbo cars? I had always heard the 4.44 was a little on the weak side and stay away from it on the turbo and be careful with some 2.5s. With the 2.2 it's the best thing we've put it the car. The current trend seems to be cracked diff carriers though.

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-KTurner
Stomp down on the exhilarator and hold on to the wheel.

Non turbo would probably be OK. For example, Pat Richard could get 4 rallies out of a 2.5RS tranny but when we switched to the WRX in 2001 we had to rebuild transmissions after every event. Longer events we actually changed transmissions every day, and the WRX transmission was stronger than the old 2.5RS unit.

We never had an issue with a lightly modded NA 2.5 (cams). My driver is also not usually hard on equipment.

I usually shift really gently .. but hmm... While i'll have a spare transmission and rear diff. they are gonna be 4.11 and with an open front diff.

what breaks the Ring and Pinons too much torque combined with rough shifting?

picture of the 4.44 front:


the old one is buried somewhere in the garage, maybe I can dig it out later.

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-KTurner
Stomp down on the exhilarator and hold on to the wheel.