2.5rs transmission & EJ207?

[Canadian818]

So I've been searching for donors/parts lately. I was always set on finding a 06, for both the 2.5 and the supposedly stronger transmission. But after seeing how many of you are going with version 7&8 JDM EJ20's (including one of the test drivers), I've started to consider other options. If i source a JDM engine, could i just get everything else from a NA impreza? I'd imagine I would need a harness and ECU for the turbo engine, but would the tranny from a NA motor fit a turbo car? If so, is it the same? Is it strong enough?

Thanks, Adam

[Silvertop]

So I've been searching for donors/parts lately. I was always set on finding a 06, for both the 2.5 and the supposedly stronger transmission. But after seeing how many of you are going with version 7&8 JDM EJ20's (including one of the test drivers), I've started to consider other options. If i source a JDM engine, could i just get everything else from a NA impreza? I'd imagine I would need a harness and ECU for the turbo engine, but would the tranny from a NA motor fit a turbo car? If so, is it the same? Is it strong enough?

Thanks, Adam

02-07 NA Imprezas are considered to be full donors. Everything will work. As you noted, you'll probably need to match your harness and ECU to the engine. To the best of my knowledge (though I'm no expert), the transmissions are identical. Gear ratios may vary slightly from one year and one model to another, but the NA boxes should be basically the same as their WRX counterparts. Browse some of the older threads on this website. There has been a lot of discussion about transmissions. One caveat. A six-speed won't fit!

[Canadian818]

I feel bad for posting, forgetting i was on the internet with a plethora of subie info out there. So i now know it'll fit, and it's very common for RS guys to swap in JDM engine and keep their transmission. Still a lot of "opinions" on whether or not the wrx transmission is stronger. Some say it is, some say its identical with different gears.

[Canadian818]

02-07 NA Imprezas are considered to be full donors. Everything will work. As you noted, you'll probably need to match your harness and ECU to the engine. To the best of my knowledge (though I'm no expert), the transmissions are identical. Gear ratios may vary slightly from one year and one model to another, but the NA boxes should be basically the same as their WRX counterparts. Browse some of the older threads on this website. There has been a lot of discussion about transmissions. One caveat. A six-speed won't fit!

Thanks. I'm well aware that the 6spd won't fit, and thats exactly why i didn't bother searching on this fourm. Its been done to death, and all 6spd talk.

[Silvertop]

Thanks. I'm well aware that the 6spd won't fit, and thats exactly why i didn't bother searching on this fourm. Its been done to death, and all 6spd talk.

Well, not all 6 speed talk. There is at least one thread that itemizes the gear ratio differences from one year to another and from one model to another. I don't remember which thread it is though, so some hunting would be required. There's also been some discussion about transmission durability (some of it negative), though the discussion was based on year classes rather than models.

[Buzz Skyline]

I believe the 2.5RS has different final drive (4.11 in the RS vs. 3.9 in the WRXs, I think) which gives you better torque and lower top speed.

[Buzz Skyline]

I believe the 2.5RS has different final drive (4.11 in the RS vs. 3.9 in the WRXs, I think) which gives you better torque and lower top speed.

[Ironhydroxide]

Well, not all 6 speed talk. There is at least one thread that itemizes the gear ratio differences from one year to another and from one model to another. I don't remember which thread it is though, so some hunting would be required. There's also been some discussion about transmission durability (some of it negative), though the discussion was based on year classes rather than models.

Thread happens to be stickied.
But for your convenience. link below
"THE Transmsission Thread: " (http://thefactoryfiveforum.com/showthread.php?9909-THE-Transmission-Thread-2-0-Now-with-Pictures)

[PhyrraM]

Non-turbo transmissions are ALMOST identical. Without getting into gearsets or strength 'conversations', Subaru uses different flywheels and clutch types on turbo and non-turbo cars. Basically, use the flywheel and clutch set meant for the transmission, not the motor.

[Canadian818]

Thread happens to be stickied.
But for your convenience. link below
"THE Transmsission Thread: " (http://thefactoryfiveforum.com/showthread.php?9909-THE-Transmission-Thread-2-0-Now-with-Pictures)

Haha, yeah I seen that right after my apology post. Figured I wouldn't bother pointing out it was a useless post twice. Good thread, read every word.

I didn't see something in that thread though, what year did the type of transmissions change from I believe you called them "phase 1&2"?

[StatGSR]

Non-turbo transmissions are ALMOST identical. Without getting into gearsets or strength 'conversations', Subaru uses different flywheels and clutch types on turbo and non-turbo cars. Basically, use the flywheel and clutch set meant for the transmission, not the motor.

^ This! I had a feeling you might beat me to it!

[SkiRideDrive]

This is an interesting idea. Please forgive my ignorance but I had a few followup questions.

Since it seems the transmission will work, are the brakes comparable from the 2.5rs to the wrx?

Also, any estimates on what it would cost to source a jdm engine and wiring harness to finish off the package?

Finally, do all the jdm engines utilize a twin scroll turbo? (I love that suby burble).

Thanks!

[Silvertop]

Quote Originally Posted by Silvertop
Well, not all 6 speed talk. There is at least one thread that itemizes the gear ratio differences from one year to another and from one model to another. I don't remember which thread it is though, so some hunting would be required. There's also been some discussion about transmission durability (some of it negative), though the discussion was based on year classes rather than models.



Thread happens to be stickied.
But for your convenience. link below
"THE Transmsission Thread: " (http://thefactoryfiveforum.com/showthread.php?9909-THE-Transmission-Thread-2-0-Now-with-Pictures)

Duh -- My mother raised at least one idiot child..................:p

[Ironhydroxide]

Haha, yeah I seen that right after my apology post. Figured I wouldn't bother pointing out it was a useless post twice. Good thread, read every word.

I didn't see something in that thread though, what year did the type of transmissions change from I believe you called them "phase 1&2"?

The years vary depending on model. and sometimes split years.

the usuall cutoff point is 97-99 depending.

impreza's swapped sooner, Legacies Later.
easiest way to tell is look at the defining features in the pics posted.

[Ironhydroxide]

This is an interesting idea. Please forgive my ignorance but I had a few followup questions.

Since it seems the transmission will work, are the brakes comparable from the 2.5rs to the wrx?

Also, any estimates on what it would cost to source a jdm engine and wiring harness to finish off the package?

Finally, do all the jdm engines utilize a twin scroll turbo? (I love that suby burble).

Thanks!

JDM harnesses are more difficult to find, IWire (https://www.facebook.com/pages/IWire-Wiring-Services/115786161784988) Does a LOT of Swap wiring, and I'm sure could hook you up with a better harness, even a Stripped one for weight ;)

Brakes on the 2.5RS are smaller, but not by far (than the 02-05). there's a whole Topic in Nastisock that entails it all.

No, only certain JDM engines and models use twinscroll... Right now i'm kinda lost as to which though.

[RelfF2]

Wow, lots of good information here. What about using a 2.5rs full donor, and then adding an aftermarket turbo kit designed for that car later? I seem to remember that being a popular thing to do, or am I remembering that wrong

[Ironhydroxide]

There are a few turbo kits "designed for the car" but we aren't held to their design limitations ;)

the EJ engine is widely unchanged in many of the applications. you can bolt a wrx turbo manifold, turbo, etc onto an RS25 engine and run it.



the only other issue is the front control arms are narrower at the pivot mount. I think that it'd be fine to just make spacers and there you go, perfect setup.
though i do NOT condone the stripping of any 2.5RS unless it has been in an accident giving its life for the owner.

[RelfF2]

Haha, good point. And thanks for the info, makes perfect sense

[MJCS]

The RS transmission clutch fork pivots in the opposite direction so has a different clutch style to the wrx transmission (pull vs push type).

And the RS has a factory dual mass flywheel which wears fairly equally with the clutch, so you will find if your clutch goes its expensive. (At a workshop - My 05 2.5 rs clutch cost $2000 with flywheel work vs my 06 2.5 wrx $600 for just the clutch).

Food for thought.....

[Ironhydroxide]

HOLY ****< how is an RS25 clutch 2k?

http://www.rallysportdirect.com/ACT-Heavy-Duty-6-Puck-Disc-Clutch-Kit-Subaru-Models-inc-1998-2000-Impreza-2-5RS
and
http://www.rallysportdirect.com/Exedy-Lightweight-Flywheel-Subaru-Models-inc-1998-2001-Impreza-2-5RS

are only 1k, and i took the most expensive of each from RSD.


that said, the flywheel isn't often REQUIRED to do. most times it can be resurfaced (subaru says no, but i've never had one fail)

[MJCS]

My clutch plates separated and took out my flywheel, including machining etc. required the transmission to be completely removed from the car and this includes labour. This is obviously worst case.

I have heard several people pay over 3k for genuine subaru replacement dual mass flywheel, clutch and all the parts required.

If you were smart you would go full aftermarket and not go back to oem but I trusted a good friend who was a so called 'guru' (when I knew less about subarus)

[Ironhydroxide]

well then claiming a clutch only cost 600 for one style and 2K for another is a GROSS exaggeration. especially when labor is factored into the one, and Not the other.

Clutch type (pull/push) is important depending on what transmission you have, but a pull isn't MASSIVELY more expensive or less expensive than a push.

[MJCS]

Both included labour (as I said previously 'AT A WORKSHOP').

I think it's important for everyone to note if you stick with a dual mass flywheel it can be a very expensive problem. Subaru actually told me in the 2005 RS it was common for the clutch plates which are riveted together to shear from each other and cause damage to the very expensive dual mass flywheel (Vs single mass). Wish I still had the clutch so you could show a picture of the damage.

I think if you go down the road of using a RS transmission, a new clutch plate and lightweight single mass flywheel is the first thing that should be done. I doubt on a car like the 818 a damping style dual mass flywheel is what you want for pure performance.

I'm just trying to note my previous experience so everyone can learn from the past, not have an argument.

Good bit of info about dual mass flywheels
http://www.npcperformance.com.au/npc_revsolution_dmf.html

Good reasons why you should convert to single mass
http://www.npcperformance.com.au/npc_revsolution_dmtsfc.html