Transmission Swap/Compatibility

[PittISDTech39]

Hi All, long time lurker, first time poster here.

I know there are a few threads around about this topic, but I haven't been able to find enough information to make me feel confident purchasing a used transmission. I have an '09 Impreza 2.5I (non-turbo) wagon that has a failing 5 speed tranny and center diff. I've read a couple different things that have said I can drop any subie 5spd MT in as long as the final drive ratio matches that of the rear diff and that it matches if its a Push/Pull type clutch. Using the Rallispec chart, Ive found that my trans (TY758VC1AA) has a FD of 3.90, but I don't know if it's a push or pull. Am I missing any other pertinent info that would make a difference before pulling the plug on a used tranny? And are JDM transmissions compatible with our USDM motors (EJ253)? I've found a few JDM transmissions with the correct final drive that are alluring due to their low mileage and they tend to be less expensive. Thanks in advance for any input!

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[Jedi03]

go 6 speed an get the rear end to match!

[snow_bound26]

You have a push type clutch. You can tell by looking at the slave cylinder. If the piston points at the engine then it's a pull type. Points toward the firewall than push type.

As for FD, you have to find out if your trans is a 1:1 or a 1.1:1 (more common). 1.1:1 has a 3.54 rear diff for a 3.9 FD.

[PittISDTech39]

Originally Posted by Jedi03

go 6 speed an get the rear end to match!

Wouldn't that be nice!

[PittISDTech39]

Thanks Snow! I'll start trying to figure out if it's 1:1:1.

[Samurai Jack]

TY758VC1AA

US Impreza 2008
You have a Transfer Ratio of 1.0 and a Final Drive of 3.90.
That means you need a Rear Diff with a 3:90 ( R160 ) to match.

You have to match the transmission to the rear diff, like I showed above. All the info is on the Rallispec chart you looked at.

Can you use any USDM or JDM transmission ( 5MT or 6MT ) with a USDM motor?
The answer is "yes you can".

If you go to a 6MT, then you will need a 6MT clutch, 6MT flywheel, 6MT driveshaft, whether or not you use your current rear diff ( R160 ) or get a 6MT ( R180 ) rear diff.

[PittISDTech39]

Originally Posted by Samurai Jack

TY758VC1AA

US Impreza 2008
You have a Transfer Ratio of 1.0 and a Final Drive of 3.90.
That means you need a Rear Diff with a 3:90 ( R160 ) to match.

You have to match the transmission to the rear diff, like I showed above. All the info is on the Rallispec chart you looked at.

Can you use any USDM or JDM transmission ( 5MT or 6MT ) with a USDM motor?
The answer is "yes you can".

If you go to a 6MT, then you will need a 6MT clutch, 6MT flywheel, 6MT driveshaft, whether or not you use your current rear diff ( R160 ) or get a 6MT ( R180 ) rear diff.

I appreciate this info! I initially missed the T.R. column on the Rallispec chart but was able to pick it out eventually. The other info I was uncertain about was the rear diff, because that info is missing on the chart for this tranny part number, so you were able to identify it for me! I was able to find a low mileage JDM transmission that should work from Sunshine State JDM down in florida with all your help. Thanks again!

[PittISDTech39]

Hey guys! I've got the used wrx tranny (with the correct final drive and transfer ratio) ready to go into my 2.5i NA but something is stumping me. I'm buying a new clutch and flywheel and struggling to determine if I should use a wrx clutch and flywheel (since it's a wrx tranny) or continue to use whats recommended for a 2.5NA?
Thanks as always!

[Samurai Jack]

Did you have a 5MT in your car before?
Are you using a 5MT WRX Transmission?
What flywheel are you using?

The flywheels and clutches are different between the WRX and the 2.5i.
Since the flywheels are different, I am presuming that that is where the issues lies, but that is a guess.

You have a couple of options:
1. 2.5i Exedy 15801 - Direct replacement
2. 2.5i ACT ACTSB2HDSS - Heavy duty
3. WRX ACT ACTSB5HDSS - Heavy duty

If you have no plans for higher power, then just stick to an OEM replacement.
This would be a good time to contact a Dealer or other Subaru-specific shop and find out the actual difference between the WRX and 2.5i clutches and whether or not they are interchangeable.

Let us know what you find out

[PittISDTech39]

Originally Posted by Samurai Jack

Did you have a 5MT in your car before?
Are you using a 5MT WRX Transmission?
What flywheel are you using?

The flywheels and clutches are different between the WRX and the 2.5i.
Since the flywheels are different, I am presuming that that is where the issues lies, but that is a guess.

You have a couple of options:
1. 2.5i Exedy 15801 - Direct replacement
2. 2.5i ACT ACTSB2HDSS - Heavy duty
3. WRX ACT ACTSB5HDSS - Heavy duty

If you have no plans for higher power, then just stick to an OEM replacement.
This would be a good time to contact a Dealer or other Subaru-specific shop and find out the actual difference between the WRX and 2.5i clutches and whether or not they are interchangeable.

Let us know what you find out

Hello Samurai and thank you once again for your intel! I'm attempting to use a 5spd wrx tranny from an '08 Wrx in a 5spd 2.5i NA from the same model year. Both cars have an identical transfer ratio and final drive (as you previously helped me identify before). I reached out to a local Subi performance shop earlier and I'm waiting to hear back from them. Browsing some other forums has helped me to lean towards believing I should be fine using an OEM clutch and flywheel for my NA engine (Exedy 15801 for example) with the wrx tranny rather than using a WRX clutch/flywheel on my NA engine.