05 Spec B Transmission Swap

[WREXJake]

After going through two 5 speeds in my 05 WRX I decided to finally make the switch to a 6 speed. After looking around for about a week I came across a Jdm 2005 Spec B trans & 3.9 WRX Rear Diff with 40k on it. I plan on doing the easiest and cheapest swap I can do so I got an automatic driveshaft and since the trans doesn’t come with one, an sti shifter/linkage. I know the 6 Speed Spec B trans is similar to the STI’s but I still have a few things I’m not 100% sure about that hopefully someone can clear up for me.

Will the Sti shifter work with the spec b’s?

Can I re use my 05’s axles? ( I know you can with the sti trans but the spec b is open center diff, don’t know if this changes anything for whatever reason)

Will my 5 speed trans cross member work with the 6 speed?

Will the STI Group N mount work with the spec b trans? Pn D1010FE000

Can I still retain my 5spd starter, flywheel, clutch

(If needed)
Comp Clutch Stage 3 Segmented Ceramic
Act Street Light Flywheel

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[jamal]

Pretty sure yes to all.

[WREXJake]

Originally Posted by jamal

Pretty sure yes to all.

You think? I really wasn’t sure especially with the axles but I figured it will all be basically the same as the sti’s 6 speed because they’re essentially the same.

[JarHarms]

Originally Posted by WREXJake

my 05 WRX + Jdm 2005 Spec B trans + 3.9 WRX Rear Diff

Got a completed trans code from the Spec'B 6MT clutch housing?

Will the Sti 6MT shifter assembly work with the 6MT spec'B 6MT?
[Yes]

Can I re use my 05’s WRX axles? [05 WRX FRONT axles should be male stub axles, photos of that Spec'B 6MT should show what type it accepts, but likely you are good to go. REAR axels are not an issue since you are using a 3:900 geared R160 Rdiff that will work with your WRX rear axels.]

Will my 5 speed trans cross member work with the 6 speed? [Yes, with the 6MT trans mount.]

Will the STI Group N mount work with the spec b trans? Pn D1010FE000 [While you may be able to get away with it, that is not correct. Use any of the 6MT mounts instead (6MT factory, GpN, GpN Competition, or an aftermarket)]

Can I still retain my 5spd starter, flywheel, clutch? [Starter, yes. Flywheel and clutch, your WRX is a pull type clutch sop you could reuse them but it is not ideal. Best to use a 6MT version of those parts.]

(If needed)
Comp Clutch Stage 3 Segmented Ceramic
Act Street Light Flywheel
[What HP/TQ is your WRX generating? What are your near term HP/TQ plans? Also if you a considering those parts, then just go with 6MT versions.]

[WREXJake]

Originally Posted by JarHarms

Got a completed trans code from the Spec'B 6MT clutch housing?

Will the STI Group N mount work with the spec b trans? Pn D1010FE000 [While you may be able to get away with it, that is not correct. Use any of the 6MT mounts instead (6MT factory, GpN, GpN Competition, or an aftermarket)]

Can I still retain my 5spd starter, flywheel, clutch? [Starter, yes. Flywheel and clutch, your WRX is a pull type clutch sop you could reuse them but it is not ideal. Best to use a 6MT version of those parts.]

(If needed)
Comp Clutch Stage 3 Segmented Ceramic
Act Street Light Flywheel
[What HP/TQ is your WRX generating? What are your near term HP/TQ plans? Also if you a considering those parts, then just go with 6MT versions.]

Trans Code: TY856WVBAA

That’s a bummer, I figured it’d work. Just ordered one yesterday at Subaru.

Currently making around 330 with similar torque and I’m happy with these numbers for now.

That’s my current clutch and flywheel setup used in my 5 speed and i wanted to continue to use them because they only have a thousand miles on them.

[JarHarms]

Originally Posted by WREXJake

...That’s a bummer, I figured it’d work. Just ordered one yesterday at Subaru.
Currently making around 330 with similar torque and I’m happy with these numbers for now. That’s my current clutch and flywheel setup used in my 5 speed and i wanted to continue to use them because they only have a thousand miles on them.

If that = 5MT trans mount, yes you should get the right mount. I googled your D1010FE000 part number and that is for the 6MT version of the STI GpN trans mount. So you should be okay after all. Just keep in mind that STI does not implicitly = 6MT.

If that = your existing 5MT flywheel and clutch, yes you can re-use them. I recall you have to match the 5MT or 6MT version TOB fork, they look similar but are different.

Trans Code: TY856WVBAA MY2005 JDM Leggy Spec'B
1st / 2nd / 3rd / 4th / 5th / 6th / TR / FD / cdiff / fdiff
3.636 / 2.235 / 1.521 / 1.137 / 0.971 / 0.756 / 1.100 / 3.900 / 4kgf Vis / open

You might want to check on this since you noted it comes with a 3.900 Impreza R160. Typically it requires a 3.540 ratio Rdiff to operate correctly with a 3.900 FD trans using 1.100 TR gears.

I would also open the extension housing to look over the Cdiff. If it is a cir-clip version then have it tack welded. If it is a newer (doubtful, those came out well past CY2005) c-clip version then leave it as-is. Might save you from a Cdiff and TR gear failure in the future.

[jamal]

The difference between the 5- and 6-speed mount is a few mm of height. Like, 3. 5 tops. Cusco just gives you a set of washers to stick between the mount and subframe on 5-speeds. I think it should be fine.

I've had a 5- and 6- speed fork and tob next to each other fairly recently, there was a slight difference between the forks but I basically couldn't tell which went to which without knowing ahead of time. Either will still fit and work if you don't have the fork with the new trans.

[JarHarms]

True it is workable but I would not recommend it. 6MT to trans tunnel is a pretty tight fit in some chassis. A few less mm is all it takes to get a fun noise during operation, or rubbed wire harness a few miles later on.
I can't recall which TOB fork combo it was but one way it can operate ok, the other it will not operate the clutch right.

[WREXJake]

Originally Posted by JarHarms

If that = 5MT trans mount, yes you should get the right mount. I googled your D1010FE000 part number and that is for the 6MT version of the STI GpN trans mount. So you should be okay after all. Just keep in mind that STI does not implicitly = 6MT.

If that = your existing 5MT flywheel and clutch, yes you can re-use them. I recall you have to match the 5MT or 6MT version TOB fork, they look similar but are different.

Trans Code: TY856WVBAA MY2005 JDM Leggy Spec'B
1st / 2nd / 3rd / 4th / 5th / 6th / TR / FD / cdiff / fdiff
3.636 / 2.235 / 1.521 / 1.137 / 0.971 / 0.756 / 1.100 / 3.900 / 4kgf Vis / open

You might want to check on this since you noted it comes with a 3.900 Impreza R160. Typically it requires a 3.540 ratio Rdiff to operate correctly with a 3.900 FD trans using 1.100 TR gears.

I would also open the extension housing to look over the Cdiff. If it is a cir-clip version then have it tack welded. If it is a newer (doubtful, those came out well past CY2005) c-clip version then leave it as-is. Might save you from a Cdiff and TR gear failure in the future.

Shoot the rear diff situation kinda sketches me out now ahaha

[JarHarms]

Since it comes with the 3.900 R160 and you have a 3.540 R160 in your WRX already..you're covered either way. If it was me I would still pull the extension housing off to inspect the Cdiff. This is also a good time to count the TR gears to confirm if 1:000 or 1:100 ratio is installed.

[WREXJake]

Originally Posted by JarHarms

Since it comes with the 3.900 R160 and you have a 3.540 R160 in your WRX already..you're covered either way. If it was me I would still pull the extension housing off to inspect the Cdiff. This is also a good time to count the TR gears to confirm if 1:000 or 1:100 ratio is installed.

There’s no other way to tell? I’m horrible with trans stuff IE this thread

[WREXJake]

So I got the swap done and ran into some major problems, first problem being the throw out bearing not seating into the pressure plate like it should I don’t know if that is from me removing it incorrectly or what but it’s not seating and I need to pull the whole trans again. Another problem that I can’t seem to find any clear answer on is I used my 5mt clutch fork, pin as well as clutch and flywheel. Is this setup correct? Or should of used the 6mt fork instead ?? Third question is my wiring harness from my 5mt has an extra connector for the speed sensor but where the sensor would be looks like it’s blocked off?

[JarHarms]

5MT vs 6MT fork issue I really have not closely compared so I'm not much help there. *I scanned through some older threads and it appears using a 5MT fly/clutch/tob in a 6MT does need the 6MT release fork or else engagement issues. But that is only what I had read...you might want to do some reading through those 6MT swap stickied threads.

The 6MT VSS is on the clutch housing. A 5MT VSS is on the side of main trans case and uses an additional extension harness. Look on the RHS of the clutch housing opposite the starter. Is there a black VSS sensor located there? Since your chassis harness was built for 5MT you will have to reuse the extension harness and coil up the extra length.

I would suspect your Neutral Position Sensor is the same function type as the one your WRX ECM requires. I would still confirm it and if not the same then swap in the one off your 5MT. And no matter what someone might suggest it is NOT a reverse the wires sort of fix.

*There are some 6MTs (newer versions) that have no VSS at all since the ABS system supplies a VSS value to the ECM/cluster. I doubt this is what you have though.