2003 WRX diff specs

[nlldavies]

I've recently bought a 2003 bugeye Impreza WRX for rallying. Its a GDA Model 80 on the logbook and currently has a 5 speed gearbox.

I've done a few searches online to see what the diff setup is on this so that I can see if I need to plan LSD upgrades for it.

Can anyone tell me what the diff specs on this model are or point me in the right direction please?

Thanks
N

[ScoobieWRX]

Model Turbo: 2.0 L
Transmission type: 5MT
Clutch type: DSPD
Gear ratios: 1st 3.454 / 2nd 1.947 / 3rd 1.366 / 4th 0.972 / 5th 0.738 - Reverse 3.333
Reduction gear(Front drive): Final reduction - Type of gear / Hypoid - Gear ratio — 3.900 (Front Diff)
Reduction gear (Rear drive): Transfer reduction - Type of gear / Helical - Gear ratio 1.100 (Centre Diff)
Reduction Gear (Rear Drive): Final reduction - Type of gear / Hypoid - Gear ratio 3.545 (Rear Diff)

P.S. Your rear diff is an LSD and pretty indestructible at that. Unless you want to change diff ratios leave the rear as is.

Your front is more of an open type but even still it's pretty damn strong too and rarely hear of one dying.

The only way you are going to go LSD on a newage 5spd is to fit a 6spd diff that gets modified/machined to fit the five speed casing. But there is no point unless you upgrade the first 4 gears and leave 5th as is. I don't rate ppg upgrade as i've heard of plenty going pop at less than 400lbft, so i'd look at alternatives.

IMHO purchasing a 6spd conversion is the way to go. The box is rated up to 600lbft and comes with an LSD. If you want DCCD go for a 2005 box with all the bits and DCCD controller.

Edited by ScoobieWRX on Monday 22 October 18:52

[nlldavies]

Thanks Scoobie, that's a great help.

Got my eyes peeled for a 6 speed.

N

[ScoobieWRX]

You'll need the drive shafts, gearstick to gearbox linkage and propshaft as well to complete the job. You may not need the rear diff as i'm sure your UK WRX has the same ratio rear diff as a UK STi. However, if you get the option of buying the diff as well, if it's off the same car, you should do so as some STi i've come across have a 3.900 final drive, but the majority of UK STi i come across daily have the same 3.545 final drive as your UK WRX.

Agreed, much easier just to do the swaps. Same priority for the gearbox, from a low mileage as possible vehicle.

Good luck with it

eBay is a good place to look.

[WeirdNeville]

I did some digging when I had my subaru, but never really got to the bottom of it: If someone could confirm:

As I understood it, the WRX had a Viscous LSD at the rear, and a Viscous "locking" ventre diff, and an open front diff. The combined effect of these was that if either front wheel lost traction the differential axle speeds across the centre diff caused it to lock and split torque 50/50 - with the Rear LSD acting as it normally would.

Am I way off the mark here? I couldn't ever get to the bottom of what combination of diffs subaru put where in the WRX's. They made a big play of the diff types in the Stis.

[ScoobieWRX]

The WRX is permanent 50/50 split (subaru quoting) regardless of traction loss at the front or rear. In reality and theory applied it's a slightly different ball game although it doesn't suddenly alter the amount of torque back and front like an STi with DCCD on Auto that can send up to 65% of the torque to the rear diff.

STi's are fitted with Suretrack diffs which were the same diffs as used on the full on rally cars? I think this is why they made such a big deal of it.

Here's the theory: http://www.clubwrx.net/forums/sti-transmission-dri...

It's an interesting read.