WRX Tranny question...

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 7:02 am

OK, I just had a quick few questions.

1) Will our 1:1 center diff bolt to the back end of the WRX transmission case?

2a) What is the front final drive in the WRX?

2b) If it's not the same, can I swap the front diff from the Legacy into a WRX case?

Reason I ask, WRX cases are cheap, and readily available. So I could have the tranny built, then just swap it out, instead of having my car AWOL for a few weeks.

206er · Post by **206er** » Sun Jan 30, 2005 9:21 am

vrg3 · Post by **vrg3** » Sun Jan 30, 2005 4:00 pm

The FSM says the front final drive is 3.900:

http://www.graphics.cornell.edu/~v/pics ... earing.png

dzx · Post by **dzx** » Sun Jan 30, 2005 4:31 pm

3.9

I'm thinking about swapping an RA gearset into mine but it wont be until fall.

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 4:40 pm

Sweet, so I could keep the front diff and still use my LSD rear end. If our center diff bolts up, then all should be good

.

I'm probably going to go straight cut, dog engagement 1st and 2nd, and straight cut, synchro'd 3rd and 4th. Stock 5th. With stainless steel shift forks. I don't think I want a full dog box, but 1st and 2nd would be cool. It will be nice to be able to downshift to 1st at any speed, and more importantly be able to launch like mad, and hard shift to 2nd.

evolutionmovement · Post by **evolutionmovement** » Sun Jan 30, 2005 5:17 pm

Sounds like a cool idea. I was thinking of something similar. While you're at it, Phil, you could put a front LSD in.

Steve

THAWA · Post by **THAWA** » Sun Jan 30, 2005 5:55 pm

The front is 4.111 for automatics.

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 8:34 pm

Yea Steve, I could! That would be wicked easy at the time, because it'd all be apart and WRX LSD's are easy to find. I wonder how much a PPG center diff's go for? I could get a beefier-than-stock, or perhaps torsen style, center diff.

Mmmm Helical front, dogged 1st and 2nd straight cut, straight cut with steel synchro'd 3rd and 4th, steel shift forks, helical center diff, vicious rear diff, man, that would be a drivetrain to end all drivetrains. It would be pretty harsh, but worth it.

THAWA · Post by **THAWA** » Sun Jan 30, 2005 8:38 pm

a rear differential wont work in the front differentials space or did you mean wrx aftermarket?

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 8:39 pm

I never said anything about using a rear diff in place of the front diff....?

THAWA · Post by **THAWA** » Sun Jan 30, 2005 8:40 pm

i edited

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 8:43 pm

Oh, WRX aftermarket. Probably something like a KAAZ.

Or, if money allowed, I'd just run a full PPG front, center, and rear diff setup. Keep the 3.9 final drive, and just have a longer 1st gear by a little bit. 1st is FAR to short in our cars. Probably run WRX ratios, so I wouldn't be killing myself with the larger wheels/tires.

Post by **Legacy777** » Sun Jan 30, 2005 9:58 pm

The 1.1:1 stepper is in the rear transfer drive & driven gear. You can simply take the rear transfer drive & driven gear out of the legacy and put it in the wrx case.

Here's a blow up of everything
http://www.main.experiencetherave.com:8 ... ension.jpg

BAC5.2 · Post by **BAC5.2** » Sun Jan 30, 2005 11:44 pm

So in that diagram, press out 25 and 36 of the legacy, and press them onto the WRX t-case shaft?

Sounds like a winner.

evolutionmovement · Post by **evolutionmovement** » Mon Jan 31, 2005 12:18 am

This may be my route with the exception of the steel synchros on the high gears. I could do the AWD conversion with a total used drivetrain while building the transmission. Where do you get a taller 1st gear? I also agree that 1st is too short (and I have a 3.7 FD), 2nd is a little short, but OK and I like the rest. Maybe a slightly taller 5th or tall 6th (for overdrive highway use only).

The straight cut gears always whine, though, right? That may be too annoying for me all the time. Is there a beefy helical set up?

Does anyone know how much of a PITA it is to set up gear lash in a gearbox? Sounds like serious aggravation (which would explain why few but specialists bother with transmissions), but I don't mind some aggravation as long as it's doable. I've been uninspired writing lately and wish I had a time-killer like that. Hell, I even cleaned my apartment I'm so bored (that and Angela wanted to stop by and I can't have her thinking I'm a filthy scumbag just in case).

Steve

BAC5.2 · Post by **BAC5.2** » Mon Jan 31, 2005 12:53 am

Steve -

Straight gears whine when power is applied to them (based on the gear profile). Any gear wider than stock (which is really narrow) will whine more than stock. In 5th, it doesn't whine at all, but in 1st through 4th, it's like a really really aggressive supercharger whine. Livable, for sure.

Beefy helical gears still whine (again, judging by a WRX i've ridden in with a helical dogbox).

PPG makes full dog sets in both helical and straight cut, and they make full synchro sets in both helical and straight cut. My friend has the PPG straight synchro'd gearset. It's really nice.

They also make half sets, so you can have dogged 1 and 2, and synchro'd 3rd and 4th.

You can get custom ratios if you really want, but they offer a few setups. I can't remember exactly what ratios my friend has, so I'll check with him and see what he got.

A slightly longer gearset would help 1/4 mile time, as well as make a more versatile gearbox. Slightly longer in the gears, means more time making big power, and less time not making power. Half of the drag automatics are 2-speed power-glide setups. Hennessy sells built Vipers with the 2-speed auto setup.

Post by **Legacy777** » Mon Jan 31, 2005 4:18 am

BAC5.2 wrote:So in that diagram, press out 25 and 36 of the legacy, and press them onto the WRX t-case shaft?

Sounds like a winner.

No need to press anything out, just remove the two shafts from the legacy box, and use them in the WRX case/setup.

BAC5.2 · Post by **BAC5.2** » Mon Jan 31, 2005 4:25 am

OOOOHHHH, sweet. Easy

legacycentral bbs

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

WRX Tranny question...

WRX Tranny question...