06 Drivetrain in my 04 WRX?

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02SilverWRX
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06 Drivetrain in my 04 WRX?

Post by 02SilverWRX »

Hey everybody, i havent posted on here in a while due to the crash. Anyways, Right before the accident, my synchro went bad in my transmission on 2nd and 5th gear. Anyways, i had just put a new differential in the rear as well and it felt great when it was done until the tranny went. To make a long story short, a buddy of mine from nasioc who lives right down the road from me did a 6 speed swap into his 06 wrx after about 10k miles. He is willing to give me his 06 wrx track models 5 speed manual (different ratio), driveshaft, rear diff, front and rear axles and install it all for $1200. Is this a good deal and also what will be the difference between the two trannys? I understand his was made for the 2.5 WRX since its an 06 and so im sure the ratio is set up for a little more power. Will this make the 0-60 times any slower or any other times slower or faster? Any idea based off of that gear ratio and that is the 3.93 ratio right?
2004 335 AWHP WRB WRX Stage 4
2005 525 AWHP AW STi
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zaxrex
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Re: 06 Drivetrain in my 04 WRX?

Post by zaxrex »

I don't think the gear ratios themselves have actually changed from mine ('02) to yours ('04) to '06. They should be 3.454 1.947 1.366 0.972 0.738. I think the difference comes from the final drive. Yours and mine have a 3.9 and I think they changed the '06 to have a 3.7. I can't be for sure, but I seem to remember that. That is going to let you stay in gear a bit longer which will take advantage of the larger torque in the 2.5 motor. Compared to your trans, it will be a bit slower on the drag, but you will be getting better gas milage.

The '06 has an upgraded double cone synchro for 1-2 compared to mine, but not sure about yours. The gear teeth are also a bit wider. Some say they are harder to bust up, but I don't see how that actually helps the gear engagement on a helical cut set...

A good deal for a used trans would be between 700-800. Axles for about 80, rear diff from 80-120. A trans swap would cost between 500-700 labor, depending. His is a pretty good deal, but it might not be what you want performance wise.

If you want to up your performance for the cheap, a 4.11 or 4.44 ring and pinion in the transfer case and a matching rear diff would cheat you into shorter gears and faster acceleration. If this one does have a 3.7, you will be making your torque work that much harder.
Patience is the ability to idle your motor when you feel like stripping your gears
02SilverWRX
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Location: Fredericksburg Virginia

Re: 06 Drivetrain in my 04 WRX?

Post by 02SilverWRX »

Hmm, 4.11 or 4.44 rack and pinion you said i think? Well my transmissions synchros went bad in 2 and 5. So if i was to buy a 4.11 or 4.44 rack and pinion what else would i have to replace other than the rear diff and how hard is that to change?
2004 335 AWHP WRB WRX Stage 4
2005 525 AWHP AW STi
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zaxrex
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Re: 06 Drivetrain in my 04 WRX?

Post by zaxrex »

Ring and pinion, not rack and pinion. One is for trannys, one is for steering :wink:

Easiest solution is to grab a Forester tranny and a R-160 rear diff to match the 4.44 with the Forester's 1:1 transfer. Call it $1400 for parts and labor.

Tougher is to take your existing trans to a shop that has the Subaru specific backlash and tolerance tools and have them install the ring and pinion, swap a 1:1 transfer in and get an Outback Sport or other 4EAT rear diff to match. A trans build can run $700 in itself in labor...Not something an amature like me would do right the first time.
http://forums.nasioc.com/forums/showthr ... ing+pinion

If things go well, I'll have the former solution done in my '02 WRX and when you are able to go out for a ride, I'll show you what it is about.
I'll post up more info when I find my manuals and instruction links.

Fast recovery and qucik mending.
Patience is the ability to idle your motor when you feel like stripping your gears
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drwrx
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Re: 06 Drivetrain in my 04 WRX?

Post by drwrx »

zaxrex wrote:Yours and mine have a 3.9 and I think they changed the '06 to have a 3.7. I can't be for sure, but I seem to remember that.
Zak is correct, the 06-07 were 3.7. And it was first gear in the transmission that received the dual-ring synchros.
And just to make things more interesting, the 08-09 have gone back to the 3.9, however, the gear ratios are slightly wider in the low gears. The 08-09 WRXs are far more similar to Legacy GTs than previous WRXs.
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