6MT Master Swap Thread

My only thing about high mileage transmissions is the bearings. Those things are probably howling if the trans has been beaten on. That being said though. If you are getting it for a dumb good deal, like sub $1500, then I would get it.

What do people think of getting a higher mileage 6MT out of a spec B with a blown motor? There are two for sale near me with about 220,000km and I kind of want to do a full spec B conversion with one of them and one of my OBXT's.

 

I believe the OBXT has a different carrier bearing support then a Legacy GT, other than that, depending on how long you plan the keep the car, having a shop check out the 6mt first may be worth it in the future years of driving enjoyment.

I did a lot of reading but not 100% certain. It seems like a +2008 6MT STI transmission should be a direct swap(with exception of DCCD) into a 2007 spec. B. The area around my clutch fork broke and I have to either replace the bell housing or swap in a new transmission:mad:.

I would think that is correct. And if you want the DCCD get a hold of DCCDPRO.

 

Only other question would be the rear diff ratio......

 

Everything else should bolt right up I would think

I believe the OBXT has a different carrier bearing support then a Legacy GT, other than that, depending on how long you plan the keep the car, having a shop check out the 6mt first may be worth it in the future years of driving enjoyment.

 

I ran the STI 6 speed in my car with a 4EAT automatic out of a legacy/GT.

 

The carrier bearing support is about an inch lower on the outback bearing.

 

Might be able to space it down if using a legacy or legacy GT shaft.

 

With that said I did not have any vibration issues at all using a legacy shaft.

 

If you want it 100% correct though I would use a 4EAT automatic shaft out of a Outback 2.5i which should have the correct carrier support bearing.

I would think that is correct. And if you want the DCCD get a hold of DCCDPRO.

 

Only other question would be the rear diff ratio......

 

Everything else should bolt right up I would think

 

 

I assume the diff ratio should be the same, since the '07-09 spec. B diff part number is the same as the late MY '07 - 2019 STI rear diff.

I assume the diff ratio should be the same, since the '07-09 spec. B diff part number is the same as the late MY '07 - 2019 STI rear diff.

 

 

Yep

What trans mount are people using when swapping an STI 6 spd into their BL model chassis? The 2007-09 Spec B specific one? pn 41022AG160 ? It is different than the 5MT mount for same years. I am running into issues with the Whiteline KDT956 insert for the spec b mount is why I ask. I assume it's not the same as 6 spd impreza sti mount as well.

 

Thanks

 

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Subaru D1010FE000 Transmission Mount

I used the Group N 6-speed mount on my stock 5mt cross member.

I used the Group N 6-speed mount on my stock 5mt cross member.

So you swapped to an STI 6 spd transmission as well? What I'm getting at is the spec b mount is different, probably due to a difference in the lgt 6 spd transmission housing dimensions vs an STI 6 or LGT 5spd mount.

 

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I think all 6MT housings are the same. It’s the gearing and tail section that are different (dccd vs non dccd) Edited March 30, 2020 by Code

So you swapped to an STI 6 spd transmission as well? What I'm getting at is the spec b mount is different, probably due to a difference in the lgt 6 spd transmission housing dimensions vs an STI 6 or LGT 5spd mount.

 

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Spec B mount or StI mount should work with your 5 speed crossmember.

 

The part numbers for the group N the 08 up STI and the spec b should be found in this thread and all three work because they all connect to the 6 speed.

 

Code is correct Both spec B and STI 6 speed are the same except for DCCD. You can even add DCCD to a spec B transmission if you wanted to

I typically create threads like this after the stuff gets installed, but I'm making an exception in this case because I need a place to take notes while I sort through the information that is sprinkled throughout the "6mt master swap thread" (and others) so that the next person to undertake this swap won't have to go on an easter-egg hunt to learn what they need to know.

 

There are two main recipes for 6MT swaps. They key difference between them is the rear diff ratio. Both use 3.9:1 front differentials, but the later transmissions have a 1.1:1 ratio on the rear output shaft, which requires a 3.54:1 rear diff.

 

Recipe A - 3.90 rear diff

Transmission options: 04/05 STI*, or 08/09 Spec B

Rear diff options: 04/05 STI, possibly 07-09 Legacy GT R160**

Rear axles: 07-09 Spec B (axles 28421AG03B, axle seals 806732200)

Front axles: Regular LGT***

Driveshaft: use a Spec B driveshaft, and replace the differential's input flange with the R160 flange.

(The Spec B R180 has an R160 input yoke, but is only available in 3.54:1.)

 

Recipe B - 3.54:1 rear diff

Transmission options: 06+ STI (I don't know what the upper bound is, but unclemat used an 08)

Rear diff options: 02-05 WRX R160, 07-09 Spec B R180*****

Rear axles: Regular LGT with R160, Spec B axles with R180.

Front axles: Regular LGT

Driveshaft: Spec B****

 

Note that there are two versions of the Spec B 6MT transmission and they have different final drive ratios.

 

* Some 04 STI transmissions need minor changes for LGT front axles - click here for more info.

** I have conflicting information about which Legacy GT R160s have which ratios.

*** 04 6MT will need new axle seals to use LGT front axles. (Part numbers here)

**** Per Z0rro, an 05-09 4EAT driveshaft can substitute for a Spec B driveshaft.

***** Cars101.com says the 08/09 Spec B uses a 3.9 final drive, however that apparently includes the 1.1 reduction in the transmission.

 

Small parts: (needed for either recipe)

 

Please confirm these part numbers for your particular transmission.

Most of these are just what I used for my 05 STI 6MT swap; later years may have differences.

 

Keep your 5MT neutral sensor switch, put it in the 6MT.

6MT shift linkage (Preferably Spec B; the Impreza shift linkage is shorter) (Is this still true for 08+ Impreza?)

6MT clutch fork - 30530AA050

6MT clutch release shaft - 30532AA020

6MT clutch slave cylinder - 30620AA172 - alternate:30620AA173

6MT clutch hose

6MT throw-out bearing

6MT rear transmission mount (same part for Spec B and Impreza)

Reverse lockout cable - 35060AG010

Downpipe support bracket - 44021FE030

R180 diff mount from the spec B - 41310AT040 (not strictly necessary, but click here for some info)

Clutch fork shaft plug (threaded cap that holds the fork shaft in) - 30550AA000 for 04-07, and 11021AA010 for 08+

Output Shaft Oil Seal (oil seal for the driveshaft interface) - 806735210 - $11.50

Clutch fork spring (spring that connects clutch fork to bell housing) - 30546AA060 - $5.20

Inner shift boot (foam/rubber, mostly for noise insulation, you can reuse the 5MT if you trim it)

If you get a DCCD diff, you'll need an aftermarket DCCD controller.

 

Courtesy of ShockerGT:

If you have an STI shift linkage, the shift lever will not be centered as the STI shifter rod and shifter stay are shorter than the Legacy parts. So, you'll need these:

 

Spec B Shifter Rod: 35041AG020

Spec B Shifter Stay: 35031AG020

 

Stick with 04-07 STI shift levers, as the 08+ versions are not compatible.

 

 

What you DON'T need:

 

Vehicle speed sensor - the LGT speed sensor is not on/in the transmission.

6MT rear transmission crossmember (same part for 5MT, just needs the 6MT mount (the rubber part))

 

Considerations: (which recipe is right for you?)

 

The Spec B 6MT has a 50/50 torque split, lacks DCCD and has an open front diff, but is less expensive

04/05 STI 6MT has a 35/65 torque split, open center diff, and DCCD

06+ STI 6MT has a 41/59 torque split, helical center diff, and DCCD

R180 rear diffs are stronger than R160 rear diffs.

The Spec B R180 uses an R160 input yoke. Not sure how much this affects strength.

Unclemat opines on differential technology.

And so does Homemade WRX.

 

Last but not least, the Spec B 6MT gear ratios are more evenly spaced than the USDM STI 6MT ratios, and they're a bit taller. Rallispec will install them into STI transmissions, and they call it a "high speed" gearing option. I did it mostly for the even spacing. Better mileage would be a nice side-effect if I stayed out of boost, but how likely is that?

 

 

Reference material:

 

Hammer Down's thread: http://legacygt.com/forums/showthread.php/sti-6-speed-swap-05-gt-61199.html?t=61199

sti_lusts's thread: http://legacygt.com/forums/showthread.php/6-speed-transmission-conversion-my-05-54771.html?t=54771

LegacyGT.com 6MT swap thread: http://legacygt.com/forums/showthread.php/6mt-master-swap-thread-107137.html

BDII's NES 6MT swap thread: http://www.newenglandsubarus.com/forums/showthread.php?t=13187

NASIOC.com 6MT swap thread: http://forums.nasioc.com/forums/showthread.php?t=1201152

An Impreza 6MT swap: http://forums.nasioc.com/forums/showthread.php?threadid=872902

A thread with some DccdPro info: http://forums.nasioc.com/forums/showthread.php?t=2032099

Info about differential types: http://forums.nasioc.com/forums/showthread.php?t=423584

Spec B shifter assembly: http://opposedforces.com/parts/legacy/us_b13/type_12/manipulation/manual_gear_shift_system/

 

Part sources:

 

Millenium Auto - http://www.y2kimports.com/ (Used Subaru parts, including 6MT transmissions)

Silverline Automotive - http://www.silverlineautomotive.com/ (6MT swap packages)

Thrash - http://www.thrashdriveshaft.com/ (custom driveshaft, $650ish)

Spiider - http://www.dccdpro.com/ (Aftermarket DCCD controller)

SGP - http://www.subarugenuineparts.com/ (Axles, seals, clutch fork, etc)

 

Instructional video:

duplicate post here, please delete Edited April 10, 2020 by SpecDubC

Spec B mount or StI mount should work with your 5 speed crossmember.

 

The part numbers for the group N the 08 up STI and the spec b should be found in this thread and all three work because they all connect to the 6 speed.

 

Code is correct Both spec B and STI 6 speed are the same except for DCCD. You can even add DCCD to a spec B transmission if you wanted to

I have the Crossmember from the 6spd spec b now installed though I'm pretty sure if you look at the parts diagram, everything but the trans mount itself are the same part number. Specifically look up 41022AG160 on Subaru oem parts site and it will tell you that the application is only for 07-09 spec b. It doesn't say it's the same as the sti one. I'm guessing the sti one would 'work' but if the original equipment manufacturer didn't use the same part, there must've been a specific reason as it wouldn't make sense for them to not use the same one if they could. Given the spec b is the only oem 6spd BL Legacy from the factory, then that's the part I'm assuming that's going to be the best fit if what you are saying is true about the housing geometry being the same for the sti vs spec b trans. The mounting dimensions on the Impreza cross member are likely slightly different than the BL Legacy, probably not to a noticable degree.

 

Since I couldn't use the insert today I just used a DIY urethane casting compound I bought via Suspension.com. I went with the 80A High Performance black option. At the worst if it's not perfect it's going to sure up the support to some degree. Pics below, it should fully cure in a week.

 

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My 05 turbo Baja 5mt ADF 2” lifted with 300whp 15” gold black rhino boxer wheels with BFG KO2s is in the process of getting a 04 Sti 6speed. So i have a few questions for anyone with answers. This may have been covered in the 164 pages of this thread (i am currently reading) so I’m sorry if I’m asking again. So here is where i am now.

In the rear.

Installed...

Baja/STi hybrid rear axles with suberdaves races.

04 r180 rear diff

Not sure if the (tail shaft?) has been changed yet. Gotta look later.

 

04 Sti 6 speed is in and bolted up

(I think 03)wrx front axles Are in.

 

So here are my questions.

 

1. So my stock 5mt driveshaft wont fit. And i knew that but it is pretty close compared to the auto trans driveshaft i got. It is way short. The stock driveshaft is just a little to long and the carrier bearing mounts are about an inch or 2 to far back from the stock holes. The short drive shaft i have i just way to short. Like 5 inches or something. I didn’t get the drive shaft myself so i am currently checking what it came out of. So it needs to be an auto driveshaft sure but out of what? legacy,gt,coupe,outback,wagon, Impreza, Baja. I have no idea.

 

2. For the trans mount i used the Sti bracket with the Baja rubber bushing thing. It’s in..... but it ain’t right. the bracket holds the trans way to high in the back. So the engine is even tipped forward a little. Also the shifter linkage is hitting the trans tunnel. I saw other people ordering different linkage but the stock Sti stuff might work? If the trans was in the right spot. I’d much rather not get linkage if I don’t really need to. So what am i doing wrong? Should i just make spacers and lower the whole bracket?

 

3. I keep reading i need a Sti clutch slave. I have one but i have the stock Baja turbo one in and i looks good. I haven’t tried to push the clutch in yet. Why would this matter?

 

Well that’s what i got for now any and all help would be greatly appreciated.

My 05 turbo Baja 5mt ADF 2” lifted with 300whp 15” gold black rhino boxer wheels with BFG KO2s is in the process of getting a 04 Sti 6speed. So i have a few questions for anyone with answers. This may have been covered in the 164 pages of this thread (i am currently reading) so I’m sorry if I’m asking again. So here is where i am now.

In the rear.

Installed...

Baja/STi hybrid rear axles with suberdaves races.

04 r180 rear diff

Not sure if the (tail shaft?) has been changed yet. Gotta look later.

 

04 Sti 6 speed is in and bolted up

(I think 03)wrx front axles Are in.

 

So here are my questions.

 

1. So my stock 5mt driveshaft wont fit. And i knew that but it is pretty close compared to the auto trans driveshaft i got. It is way short. The stock driveshaft is just a little to long and the carrier bearing mounts are about an inch or 2 to far back from the stock holes. The short drive shaft i have i just way to short. Like 5 inches or something. I didn’t get the drive shaft myself so i am currently checking what it came out of. So it needs to be an auto driveshaft sure but out of what? legacy,gt,coupe,outback,wagon, Impreza, Baja. I have no idea.

 

2. For the trans mount i used the Sti bracket with the Baja rubber bushing thing. It’s in..... but it ain’t right. �� the bracket holds the trans way to high in the back. So the engine is even tipped forward a little. Also the shifter linkage is hitting the trans tunnel. I saw other people ordering different linkage but the stock Sti stuff might work? If the trans was in the right spot. I’d much rather not get linkage if I don’t really need to. So what am i doing wrong? Should i just make spacers and lower the whole bracket?

 

3. I keep reading i need a Sti clutch slave. I have one but i have the stock Baja turbo one in and i looks good. I haven’t tried to push the clutch in yet. Why would this matter?

 

Well that’s what i got for now any and all help would be greatly appreciated.

 

Driveshaft wise, for the 4th gen legacies, people use either 4eat shafts or spec b shafts for the swaps. These have a r160 yoke but are the correct length for the bp/bl chassis.

 

For the 4th gen legacies the only thing that people use which is different is the physical rubber mount which has different hole spacing on the 6spds than the 5spds. The transmission subframe for the 5mt cars is reused.

 

The reason why the sti slave is used because the 4th gen legacies 5mt has a different slave which mounts completely differently and is not compatible. If you have a 02-05 5mt slave that will work as well.

 

Hope this helps.

And to add, 05-09 legacy/outback 4eat shafts. Outback shafts have a carrier bearing which drops them lower for adjusting driveshaft angles to compensate for the body spacers.

Awesome! That’s a great help. I have 3rd gen Do you think the auto BH is the same lengths as the auto BT?

I’m gonna hit the junk yard for a 3rd gen auto outback drive shaft now.

I must have been given and auto Impreza driveshaft.

I’m happy I don’t need to swap out the slave cylinder.

As for the tranny bracket and rubber mount.

I have the STI bracket with the BAJA mount. But it’s holding the tail of the tranny up way to high. The Baja vs Sti bracket looked damn near exact. I guess I’ll just pull it out and swap it and see if that cures my issue. Thanks again.

 

 

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I honestly couldn't tell you if BH and BT are the same length as I genuinely have never been under a baja to tell you if its the same car or not. But considering that their part of the same generation family I think a BH driveshaft will fit a BT.

 

Interesting that your 5MT rubber mount bolted up. I actually never tried bolting up the 5MT mount because the 6MT mount has a uniform chunk of rubber not 2 separate pieces.

Yeah the stock rubber bolts right up.

So the answers i have found.

 

1. About the drive shaft. It seems i got an Impreza auto drive shaft. I’m getting a Legacy outback BE,BH,BT auto driveshaft from the junk yard tomorrow. The distance from the front to the bearing mount should be 2 inches ish shorter and past that the same. Fingers crossed.

 

2. the trans mount. I figured its an Sti trans so I should use the Sti bracket. Wrong. The Sti bracket sits way higher on the passenger side than the stock Baja one. So i swapped the stock bracket with the stock rubber and it all bolted up happy and dropped the tail perfect. But i also found that using the stock linkage for the Sti works great but that i used the Sti mounting bracket. (That 2 bolt thing that bolts to the body to hold the tail) sits like an inch higher than the stock Baja one so i stuffed the stock mount on there and its great. In side the metal bracket that holds down the rubber boot just touches the shifter going into 1st second area so i just took a 1/4 inch off with a file.

 

3. Stock Baja clutch slave... perfect.

 

Ill do a write up on the Baja turbo 6spd swap after i get it all done. Thanks for the help.

I have the Crossmember from the 6spd spec b now installed though I'm pretty sure if you look at the parts diagram, everything but the trans mount itself are the same part number. Specifically look up 41022AG160 on Subaru oem parts site and it will tell you that the application is only for 07-09 spec b. It doesn't say it's the same as the sti one. I'm guessing the sti one would 'work' but if the original equipment manufacturer didn't use the same part, there must've been a specific reason as it wouldn't make sense for them to not use the same one if they could. Given the spec b is the only oem 6spd BL Legacy from the factory, then that's the part I'm assuming that's going to be the best fit if what you are saying is true about the housing geometry being the same for the sti vs spec b trans. The mounting dimensions on the Impreza cross member are likely slightly different than the BL Legacy, probably not to a noticable degree.

 

Since I couldn't use the insert today I just used a DIY urethane casting compound I bought via Suspension.com. I went with the 80A High Performance black option. At the worst if it's not perfect it's going to sure up the support to some degree. Pics below, it should fully cure in a week.

 

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Mind Blown

Ive been in and out of this thread over the years, but cant say ive read all of these pages, so if this has been covered, I apologize, but I believe I may have another potential solution for more easy to obtain rear axles when converting to the R180.

 

I think you are able to run STi axles (2004-2007) when installing a R180 differential in the 4th gen legacy platform if you swap to 2012+ impreza rear hubs.

 

As far as I could tell, the STi axles are nearly the same length as the Spec B axles based on this thread reply: https://legacygt.com/forums/showpost.php?p=4392808&postcount=17

 

And this image for replacement STi axles (which are less than $60 )

 

 

Next, the hubs gotta be a match aside from the drive spline, the new ones have to have 27 splines where our stock hubs have 25.

 

2012-2019 (maybe later) Impreza (and everything else on that platform that came later : https://www.rockauto.com/en/moreinfo.php?pk=5829054

 

2005-2009 Legacy Rear Hubs: https://www.rockauto.com/en/moreinfo.php?pk=1119780

 

The key differences here (aside from the spline count) is the flange offset which differs by about 1mm and the height of the bearing in the back. More on that below:

 

The 'new' hubs would push the rotor out about 1mm. This may cause some issues with both the parking brake and rear brake. I think this 1mm may be forgivable when working with new rotors and slightly worn brake pads. Who knows, it might even work with new pads on the caliper, but youd give yourself more room with slightly worn pads.

 

Secondly, that hub sticks into the trailing arm a little bit more. This poses 2 problems: axle length (which is kinda a question mark to begin with) and abs sensor. After looking at the Legacy trailing arms, you might be able to get away with drilling out the threaded hole for the screw that holds the ABS sensor in and holding the sensor in some other way.

 

Hopefully you are still with me, but I just wanted to share what I found when considering my options while looking at a potential 6MT swap. The spec B axles seemed a bit difficult to come by so I started looking at adapting the car to use more common axles. I havent tried it yet but I have enough parts laying around to try it off the car should I decide to go down this path.

 

I personally have the option of machining alot of this stuff to work, but I like to put the effort up front to try to find solutions that dont require machining of common replacement items, especially so others can employ the same solutions.