[TROLL]

Some of you may or may not know about some interesting differences with the 2006 STi Transmission... there doesnt seem to be a whole lot of info out there about it and I am trying to compile a comprehensive resource on it for myself, and others who may find it useful in the future.
I will list what I have confirmed below, and if anyone can add some more helpful information then that would be fantastic.

-All model year STis use the same Driver Controlled Center Differential, but the 2006 STi Tranny uses a LSD type center differential instead of an open differential like in the 04-05 models. This has the ability to modulate power up to 30% in either direction, even when the DCCD is set to the full "open" position.

-The 2006 STi Tranny has a 1.1:1 Center Diff, meaning the front differential final drive is 3.90, and the rear R180 differential final drive is 3.54. This is speculated to have a better mechanical torque bias than the previous 3.90/3.90 setup for the 04-05. Also said to better match the weight distribution of the car, resulting in better balance, better turn-in, and less understeer than previous models. (This also means the 2006 STi Transmission can be swapped into any WRX without any modification to the stock WRX R160 rear differential.)

-Power split on the 2006 STi Tranny is 41/59, unlike previous years where the split was 35/65.

-The 2004 driveshaft (no personal experience with a 2005) are a large diameter, hollow design. The 2006 driveshaft is similar for the most part, but has a ~1 foot section at the beginning of the rear half that is much smaller in diameter, and appears to be solid. (added 8/26/06)

-The front axles on the 2006 use a revised ABS system which incorporates a geared ring on the axle itself. From the little I know so far, this means that the front axles will not fit onto an 02-05 Impreza. (If anyone has any more info on this matter, I dont know much about it so please help out here...) (added 8/26/06)

-The 2006 tranny has carbon coned synchros on 4th, 5th, and 6th gears to help deal with heat issues on previous models. (added 8/27/07 by cliff257 on iwsti)


Thanks, and you're welcome!

Bryan

[TROLL]

nobody has any input? really trying to find out about the speedo today!

[nw-TI]

Pretty sure you need to have the same final drive at the front as you do at the back because the wheels still need to spin at the same speed...

[TROLL]

pretty sure you dont know what a 1.1:1 center diff is... a 3.9 in the front spins at the same speed as a 3.54 in the back with a 1.1 center (multiply 3.54 x 1.1, it equals ~3.9). believe me, i've confirmed everything i listed above except the one thing that was in question.

kinda shocking that a forum of sti owners exclusively doesnt know anything about the 06 sti transmission... but hey if you want to let the wrx guy teach you about it... thats cool i guess, haha.

[Private50]

that's why is posible to do rear burnouts in 04-05 than 06...Im glad i have a 05!

[stretch]

The RWD-ness of an '05 might be more fun, but having a true LSD in the center differential is surely going to result in a faster car. I only wish Subaru had installed the LSD and kept the default 65% rear torque bias.

Good topic, you get 5 stars.

[La Mer]

Originally Posted by TROLL

pretty sure you dont know what a 1.1:1 center diff is... a 3.9 in the front spins at the same speed as a 3.54 in the back with a 1.1 center (multiply 3.54 x 1.1, it equals ~3.9). believe me, i've confirmed everything i listed above except the one thing that was in question.

kinda shocking that a forum of sti owners exclusively doesnt know anything about the 06 sti transmission... but hey if you want to let the wrx guy teach you about it... thats cool i guess, haha.

sti ownerS?

you say that after one person try's to help.

[gregsachs]

Originally Posted by stretch

The RWD-ness of an '05 might be more fun, but having a true LSD in the center differential is surely going to result in a faster car. I only wish Subaru had installed the LSD and kept the default 65% rear torque bias.

Good topic, you get 5 stars.

This statement is pretty misleading. The 04/05 have a true LSD mechanism, based on a friction clutch assembly. This does, I am confident, have an overload point where it will slip despite the locking, (equivalent to breaking gears in mechanical lsd). The 06 just _added_ a mechanical LSD to complement the variable clutch system, changing it from a 0-100% locking system to a ~30%-100% locking system. That, in addition to the changed ratio, are presumably faster than the 04/05 system, but it isn't because there isn't a 'true' LSD.

[stretch]

Originally Posted by gregsachs

This statement is pretty misleading. The 04/05 have a true LSD mechanism, based on a friction clutch assembly. This does, I am confident, have an overload point where it will slip despite the locking, (equivalent to breaking gears in mechanical lsd). The 06 just _added_ a mechanical LSD to complement the variable clutch system, changing it from a 0-100% locking system to a ~30%-100% locking system. That, in addition to the changed ratio, are presumably faster than the 04/05 system, but it isn't because there isn't a 'true' LSD.

I agree, my statement was misleading. I had a brain fart and was thinking the '06 had a Torsen type differential added to them, which certainly isn't the case. I was reading about Audi's Quattro recently, so again, excuse the brain fart.

[TROLL]

Originally Posted by La Mer

sti ownerS?

you say that after one person try's to help.

i meant that i was a little surprised that i wasnt getting any responses, but apologize if that came off wrong. it was coming down to D day on dropping a lot of cash on this tranny and i was stressing because i couldnt get any straight answers. well the day came and i went for it, so now i've got a purty tranny sitting in my garage and hopefully i'll be installing it within a week or two and finding out first hand how well it works, ha. unfortunately it looks like i'm the pioneer on this situation specifically, so cross your fingers that things go well...

[krees23]

Pics?

[TROLL]

pics of the 06 tranny? if you're serious i'll be happy to take them for you. i dont have any yet because its tucked away in the corner of my garage but i really was intending to take some so if you have any specific requests let me know...
bryan

[TROLL]

added another point about the driveshaft and the front axles in the first post...

[wdb]

Good luck with your project, and by all means please keep us updated. However a quick note about IWSTI vs., say, NASIOC: we have far fewer members here, roughly 1/10 as many. So please adjust your expectations accordingly re the quickness and quantity of responses.

[cliff257]

i do know that the 06 trans has 4th,5th,and 6th gear synchros that are carbon coned. the carbon reinforcement is to help deal with the heat issues on the 04 and 05 STi's. I have installed them in my 04.