Well I PM'd Fuji K on NASIOC. He's the guy who wrote up the whole gear ratio thread. and here is what he replied to me.

"The '06 STi tranny would require to run the 3.545 rear diff. This diff can be found on all '02-05 WRX 5spd manual.


Fuji"

So does anybody have one??

I will give you mine in trade for your brembos.

Suck my left nut joel. hah ..............no homo.

Hmmm... tempting. but no.

Like I said in the other thread, I've got a non-LSD 3.545. You can swap the LSD carrier from your 3.90 into it and be all set. It's a little messy, but the swap takes well under 30 minutes... at least Cory and I were down to 30 minutes to do the swap on my SVX and that included taking the diff off the car and reinstalling it.

You could even sell the open 3.90 you'll be left with to some poor schmo that's got an older WRX who's doing a 6MT swap who can swap in his 3.545 LSD carrier. 'Course, if you can find someone doing a 6MT swap into a bugeye or something, just trade them diffs straight up.

Sounds good to me. I'll take it. That way i can start tearing the car apart now. Then when my clutch arrives.. Everything will be ready to just put the tranny on. :)

haha well that's you and cory. It may take me about....eternity.
:picard:

I just double checked the part number on the tranny.. it's an 05.. but im assuming that i'd still need the same diff and that nothing changes? I hope..

If it's an '05, I think it will work directly with the diff that's already on your car. See if you can confirm the rear diff on the '06 TR is a 3.90, cause that's what you need.

I have a 3.70FD... That's stupid..

Ouch. Didn't see that coming. WTF?

Yea. that's what I said.. I dont know what the F to do now. haha

EDIT: Nevermind, I need a 3.90FD again.. Back to square 1.

If anybody has a rear diff they want to sell out of the following car's please contact me asap!

NOTE: REAR DIFF Final drives are tranny specific
'98-01 5spd Impreza L/Sport wagon 5spd, or 5spd 95-99 Legacy 2.2L models
02-07 5spd 3.90 Impreza TS/RS wagon/outback sport
06-07 Auto WRX 3.90 VLSD

Austin, I'm pretty sure I have a 3.90 FD R160 at home. If you want to take it down and see if it is, you can pick it up at my house tonight or here at the shop tomorrow. It's in good shape and I know it's usable, I'm just not 100% sure it's 3.90 and not 4.11.

Could you possibly get me the part number off it tonight, and if it is what I need I can pick it up from the shop tomorrow before I leave tomorrow for sac.

Which vehicle is it off of?

It's from a 2000 OBS 4EAT, if it's stil the one I'm thinking of. I'll check it for part numbers tonight.

Ok thanks