what diff. to put into my FWD legacy rallyx car

greg donovan · Post by **greg donovan** » Mon Aug 16, 2004 6:22 am

as josh said my diff is a 3.70 so...

what subaru would have the best front diff ratio for acceleration?

and since it is FWD i can put any ratio up there i want right?

edit:

should i get a 4.44 one or a 3.90 one.

re-edit:the discussion has changed a bit so i changed the title and the content a bit to better reflect the direction of the conversation.

Post by **Legacy777** » Mon Aug 16, 2004 2:32 pm

All FWD's have 3.70 final drive ratio.

The more gear reduction you have the better the acceleration will be, so 4.444.

BAC5.2 · Post by **BAC5.2** » Mon Aug 16, 2004 5:57 pm

You are gonna be so limited by traction, it'll be ridiculous.

greg donovan · Post by **greg donovan** » Mon Aug 16, 2004 7:23 pm

BAC5.2 wrote:You are gonna be so limited by traction, it'll be ridiculous.

the plan is to get a 4.11 or 4.44 and get a phantom grip type conversion to help w/the traction. or if i can save enough money a KAAZ unit w/those ratios.

heck if its a 3.70 then a 3.90 would be an improvement, wouldn't it? but how much?

remember this is for rallyx use so the goal is better accelleration out of the corners and i have rally tires to add grip. and i realize that 100% throttle is not always the best answer.

evolutionmovement · Post by **evolutionmovement** » Mon Aug 16, 2004 10:01 pm

3.90 wouldn't be worth it IMO as the speed increase/rpm is small. I'd go for either of the higher ratios.

Steve

greg donovan · Post by **greg donovan** » Mon Aug 16, 2004 11:39 pm

so i want a dif from either an:

auto 2.5 (4.44), this could be abit much

or

auto wrx/2.2 l impreza 5MT (4.11), this would probably be the best compromise

THAWA · Post by **THAWA** » Tue Aug 17, 2004 3:37 am

or an na legacy.

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 3:48 am

THAWA wrote:or an na legacy.

yeah i just got off my but and dug out my owners manual and saw that the only dif between the FWD and AWD besides the AWD part is that the FWD is 3.700 up front while the AWD is a 4.111 up there.

here is the stock setup for gearing for both a AWD and FWD 5MT legacy transmission in 1990:

1st 3.545
2nd 1.947
3rd 1.366
4th 0.972
5th 0.738
rev. 3.416

the difference is in the front final reduction gear (aside from no center or rear diff. of course).
3.700 for the FWD.
4.111 for the AWD.

evolutionmovement · Post by **evolutionmovement** » Tue Aug 17, 2004 4:17 am

Let me know how it goes if you do this - I'm thinking of doing a Legacy turbo transmission to 3.700 so I can get a much easier to find 3.7 LSD from an older Subaru and get a touch more gas mileage on the highway. I figure when I finally can afford a turbo transmission and can find one I'll get it cryotreated and rebuild it.

Steve

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 4:25 am

evolutionmovement wrote:Let me know how it goes if you do this - I'm thinking of doing a Legacy turbo transmission to 3.700 so I can get a much easier to find 3.7 LSD from an older Subaru and get a touch more gas mileage on the highway. I figure when I finally can afford a turbo transmission and can find one I'll get it cryotreated and rebuild it.

Steve

what subarus had a 3.700 front LSD? and will it fit in the 90 FWD 5MT?

i would rather do that then add a turbo or a ej25 n/a.

THAWA · Post by **THAWA** » Tue Aug 17, 2004 4:31 am

he means rear LSD

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 4:34 am

THAWA wrote:he means rear LSD

since he has a 90 fwd i thought that was what he was talking about.

THAWA · Post by **THAWA** » Tue Aug 17, 2004 4:58 am

hes doing an awd conversion though

evolutionmovement · Post by **evolutionmovement** » Tue Aug 17, 2004 5:02 am

Yeah, I meant rear. I'm converting to AWD at some point. Maybe when my new job stops paying me in rupies. I'm making half what I was making before, but I guess a career change requires some work.

Steve

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 5:08 am

THAWA wrote:hes doing an awd conversion though

th thread is about FWD though

THAWA · Post by **THAWA** » Tue Aug 17, 2004 5:12 am

it's also about a legacy, but steve threw in a comment about an ea car

evolutionmovement · Post by **evolutionmovement** » Tue Aug 17, 2004 5:16 am

You asked why I wanted to switch the front diff to a 3.700 ratio and I was wondering how much of a PITA it would be so let's just call it a chicane in the thread.

Steve

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 5:38 am

evolutionmovement wrote:You asked why I wanted to switch the front diff to a 3.700 ratio and I was wondering how much of a PITA it would be so let's just call it a chicane in the thread.

Steve

no hard feelings im just being a smart ass thats all. and was a little excited about a 3.70 front LSD. but i will keep all aprised of my choice and results if i do this.

evolutionmovement · Post by **evolutionmovement** » Tue Aug 17, 2004 5:40 am

It's cool, I knew you weren't being a dick. A front LSD would be real nice, but good ones are big $$ and I'm a poor little drummer boy.

Steve

greg donovan · Post by **greg donovan** » Tue Aug 17, 2004 5:44 am

evolutionmovement wrote:It's cool, I knew you weren't being a dick. A front LSD would be real nice, but good ones are big $$ and I'm a poor little drummer boy.

Steve

the KAAZ unit is about 800 but i have seen used ones for around 500. i would love to get ahold of one of those. fortunately i dont have to change out 3 diffs to change my final drive ratio.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

what diff. to put into my FWD legacy rallyx car

what diff. to put into my FWD legacy rallyx car