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Old 01-16-2019, 09:21 PM   #1
WREXJake
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Question 05 Spec B Transmission Swap

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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Old 01-16-2019, 10:36 PM   #2
jamal
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Pretty sure yes to all.
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Old 01-16-2019, 11:08 PM   #3
WREXJake
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Quote:
Originally Posted by jamal View Post
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.
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Old 01-17-2019, 08:21 AM   #4
JarHarms
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Quote:
Originally Posted by WREXJake View Post
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.]
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Old 01-17-2019, 01:16 PM   #5
WREXJake
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Quote:
Originally Posted by JarHarms View Post
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.
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Old 01-17-2019, 01:38 PM   #6
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Quote:
Originally Posted by WREXJake View Post
...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.

Last edited by JarHarms; 01-17-2019 at 01:50 PM. Reason: good luck ;)
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Old 01-17-2019, 01:38 PM   #7
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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.
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Old 01-17-2019, 01:54 PM   #8
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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.
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Old 01-17-2019, 09:51 PM   #9
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Quote:
Originally Posted by JarHarms View Post
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
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Old 01-17-2019, 10:22 PM   #10
JarHarms
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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.
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Old 01-18-2019, 10:07 AM   #11
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Quote:
Originally Posted by JarHarms View Post
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
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Old 01-21-2019, 09:53 PM   #12
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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?

Last edited by WREXJake; 01-21-2019 at 09:54 PM. Reason: Typo
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Old 01-22-2019, 09:26 PM   #13
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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.

Last edited by JarHarms; 01-22-2019 at 09:39 PM.
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Old 11-01-2019, 11:57 AM   #14
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Will a 3.0r transmission work on an ej20 engine?
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Old 01-06-2020, 04:00 PM   #15
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What did you end up doing to get everything to work? Looking at doing a similar swap.
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Old 09-13-2022, 02:46 AM   #16
Kito818
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Lol, I was literally doing this swap the same time you were, but I threw out the engine too, screw that 4cyl crap. So 5spd push type clutch and flywheel definitely a no go, pressure plate bolts to the face of the flywheel, you're out. If you 5spd pull type clutch bolts to risers off the face of the flywheel, you'll probably be fine. I say probably because I dont know the diameter of the of the two clutch sets. Worse case I would assume you have a smaller clutch set than the 6spd version, but that's conjecture, I don't actually know. I've been building off an 09 base model Impreza platform instead of a WRX or STI platform, so I had a push type 5spd and the clutch and flywheel were very different from the clutch set found in the MY 05 Spec.b 6spd.

Mounts are... interchangeable, Subarus are called lego cars for a reason. To go further, while the automatic trans uses different mouting brackets than the manual, the bolt hole locations for both mounts are on all the bodies, so manual=>auto swap or auto=>manual swap will involve different brackets but the respective mounting locations have threads waiting for you, have fun.



Straight up bad news bears time now. As OP has probably found out the hard way by now, rear diff and trans need to be matched, don't think you're all good because you have the r-160, if you don't have the matching JDM MY05 Spec.b rear diff, you'll probably be wondering why your center diff keeps failing... hope you didn't discover this the hard why, its expensive. Starter, guess what, also specific to the JDM MY05 AND JDM MY06 Spec.b, it's 300$, direct from Japan only (if you can find it), always used, and built in a way that apparently can't be repaired (or at least easily?) No one makes a replacement for the original, probably since it was only used on one transmission each for two years, and that trans was only released in Japan. You will probably want the US STI 6spd linkage, another thing I have not actually compared is angle of the shifter, the one I have may just be bent slightly or it could be that it truely was designed to lean towards the front right seat instead of the center or front left seat. I've played around with this in my head, and it may be the hole drilled gear selection rod is what's at an angle that prefers the front right seat. If thats the case, sucks to be us, it's noticeabe.

Though this question wasn't asked by OP I'm going to answer it anyway, yest the transmissions are interchangeable between the 4cyl and 6cyl engines, at least up until 2014, after that I have no clue what the dimensions are. If I were to make a bet, they probably still bolt right up, for this question though yes, 2.0l, 2.5l, 3.0l, and 3.6l engines all share the same transmission bolt pattern between 2000 and 2014. Again these years could expand further in either direction, but my research stopped there.

I know this is an "old" thread but I hope it helps those considering the swap now. Final word, knowing what I know now the only advantage to this transmission is its final drive is faster than an STI or WRX 6spd transmission. First 4 gears are the same ratio as the STI, last 2 are longer. I know from personal experience a stock 3.0l pared with this trans will eat a stock STI or WRX and then laugh as it hits the higher speed, HOWEVER, you can order 5th and 6th gear from this trans and swap them to the STI 6spd, and the MY07 6spd was a redesign in the same case that is less prone to failure, and less exclusive. Good luck in all your endeavors!
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Old 02-21-2023, 11:25 AM   #17
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Is swapping the 5th and 6th gears straight forward or would I need other spec b 6spd parts to accomplish that? Also how is the 3.0 swap treating you?
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Old 02-22-2023, 03:18 AM   #18
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I haven't swapped the gears myself, I bought a spec.b transmission without actually understanding the problems it came with, or the advantages. That said, my second ez30 w/spec.b 6spd arrives in two days, so trust me, I'm not mad about what I have.

The spec.b vs STI 6spd varies in the gearing ratios of the last two gears, with the spec.b having the better fuel economy and higher top speed, the STI has better acceleration... in the last two gears, but more torque, which does translate to agility on the interstate. When you're already at cruising speed and you decide to press the pedal in a little further, the STI 6spd will feel more responsive faster. At least that's what the numbers say. I have a base model 09 Impreza body, even with the 3.0L/6spd swap, I'm still between 250lbs and 400lbs lighter than the STI of the same year, thats about 10% difference in body weight, enough I think the word significant applies. I haven't found an unmodified STI that can actually keep up, though truthfully I've only had 3 different STIs to compete against, so it could be a wash in the end.

Something to keep in mind, through ratio is different, spec.b TR is 1.1, STI is 1.0. Differentials are different, spec.b only has an r160 differential option, STI has both r160s and r180s to choose from, different final drive ratios ect. You know if you DON'T want a symmetrical AWD, you can mix and match, blow up a few differentials ect. I don't know for sure, but I think it's the three differentials in the car that have to match. In otherwords, your gears are probably going to interchange just fine, as long as your three differentials are properly matched.

If you couldn't tell, I really like my 3.0L lol. I've had a lot of trouble out of the Haltech until the Nexus upgrade. I have a bad center differential (knew about this and still haven't fixed it), and a bad front passenger CV shaft that made me think I blew up the front differential somehow, but I'm moving forward with the build. The only thing I can say I do not like is the two upper coolant lines and the radiator. I think I understand why they did it that way, I just don't like it and it's been a point of annoyance for me. Even so, stock(outback/legacy) radiator and fan setup fits, and the only modification for that was to drill new bolt holes for the mounting brackets, didn't have to reverse the fans or anything. Overall, I actually really really (two on purpose) like the 3.0L impreza. I'm looking forward to swapping the outback to a 3.0L/6spd as well, though I think I'm going to run a factory ECU instead of another Haltech, but still undecided there.
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