STi tranny in a WRX?

[Kyole]

hey guys, first post. I just bought an 02 wrx and im new to the wrx world but have plenty of tranny experience(remove, rebuild, replace) and i was wondering if an sti transmission will directly bolt up to a stock wrx. i want to toughen up the transmission and get that extra gear at the same time. is this possible? or are there newer sti trannys that will work?? thanks for any help.

[mosc]

Originally Posted by Kyole

hey guys, first post. I just bought an 02 wrx and im new to the wrx world but have plenty of tranny experience(remove, rebuild, replace) and i was wondering if an sti transmission will directly bolt up to a stock wrx. i want to toughen up the transmission and get that extra gear at the same time. is this possible? or are there newer sti trannys that will work?? thanks for any help.

No it won't. It's a very involved and expensive swap. The more popular and cheaper option is to go with RA gears (a little stronger) or swap in PPG gears (requires some work to the casing). A full set of PPGs will actually be stronger than the STi 6-speed anyway.

Also, the 6-speed isn't that tall. 5th on a WRX is about the same as 6th on the STi. The STi is just a much closer ratio than the stock WRX 5-speed. For example, the STi needs to use 3rd to get to 60mph.

I made this a new thread. The thread you posted in was 8 months old.


Anyway, WELCOME!

[turmic]

It can be done...but its a lot harder, more extensive, and expensive then the options mosc mentioned. IE...a gear swap out. How to do it is in the trans sticky and I've re-posted the important parts in a few threads. Search around...you'll see what we're talking about.

[Kyole]

ok, thanks guys. i think ill save up and get the RA gears, hopefully i can get it done by the start of autox season.

[turmic]

I'd only get RA gears if your not thinking about pushing the car that much. They will fail with higher than stock hp and constant abuse.

[WReXd]

Aren't the 5th and 6th gears significantly taller for the newer sti's?

[tuner ready]

for the 07, the gears are longer. That is why some people change to the 07 sti tranny

[Kjott21]

Originally Posted by Kyole

hey guys, first post. I just bought an 02 wrx and im new to the wrx world but have plenty of tranny experience(remove, rebuild, replace) and i was wondering if an sti transmission will directly bolt up to a stock wrx. i want to toughen up the transmission and get that extra gear at the same time. is this possible? or are there newer sti trannys that will work?? thanks for any help.

Originally Posted by mosc

No it won't. It's a very involved and expensive swap. The more popular and cheaper option is to go with RA gears (a little stronger) or swap in PPG gears (requires some work to the casing). A full set of PPGs will actually be stronger than the STi 6-speed anyway.

Also, the 6-speed isn't that tall. 5th on a WRX is about the same as 6th on the STi. The STi is just a much closer ratio than the stock WRX 5-speed. For example, the STi needs to use 3rd to get to 60mph.

It isn't any more expensive or difficult to swap in an STi transmission than it is to get gears worth putting in (PPG's) installed in the 5MT. For a PPG swap you are looking at right around $5K and you can do the STi tranny swap for about the same price.

Kyole:
The easiest way to do it is to get an 06/07 STi tranny and an automatic Impreza driveshaft that way you don't have to swap rearends.

If you do an 04-05 STi transmission there are a few options:

Option 1) buy an R180 and do a full 04 STi drivetrain swap (04 STi Hubs, Brakes, axles, driveshaft and 04/05 STi R180)....Most costly

Option 2) Cheapest option, buy an r160 rearend that has a 3.9 F/D and automatic impreza driveshaft, unfortunately no LSD, so you either have to swap you LSD into it or run no LSD. (typically buy the rearend for $150 at most junk yards).

Option 3) buy the 3.9 F/D ring and pinion set-up for your current R160 and have that swapped in. Typically that runs around $300 or so + install. Along with that you need an Automatic Impreza driveshaft

I got this info from another forum. Email me if you want the source.

[Danielson]

so how much taller is 07 STI than an 05 WRX trans?

[mosc]

I think 6th in the 07 sti at 6500rpms is like 155 where 5th in the wrx is like 145. Approximate.

Also, I'll re-state that the 6-speed swap is CONSIDERABLY more expensive than PPG gears. The tranny itself may go for $5,000 used but that doesn't include the rest of the parts you will need to deal with that swap. Also, the PPG would be brand new.

[Kjott21]

Originally Posted by Danielson

so how much taller is 07 STI than an 05 WRX trans?

05 WRX
1st: 3.454
2nd: 1.947
3rd: 1.366
4th: 0.972
5th: 0.738
Final Drive 3.90

05 STi Ratios:
1st 3.636
2nd 2.375
3rd 1.761
4th 1.346
5th 0.971
6th 0.756
Reverse 3.545
Final Drive 3.90

07 WRX Ratios:
1st: 3.454
2nd: 1.947
3rd: 1.366
4th: 0.972
5th: 0.738
Reverse 3.333
Final Drive 3.7

2007 STi Ratios:
1st: 3.636
2nd: 2.375
3rd: 1.521 vs 1.761 in 2006
4th: 1.137 vs 1.346 in 2006
5th: 0.971
6th: 0.756
Reverse: 3.545
Final Drive 3.9

Speed/RPM Calculator

[mosc]

forgot they changed the final drive ratio on the wrx in 07, thanks.

04-07 STi 6500rpms in 6th: 158
05 WRX 6500rpms in 5th: 162
07 WRX 6500rpms in 5th: 168 (smaller tires make up some of the diff change)

hmm, my math was off.