Tooth_Brush Posted December 4, 2021 Share Posted December 4, 2021 (edited) Hello everyone! Thank you all for taking the time to read my post and make some suggestions. I look forward to hearing from you! My car is a 2012 Subaru Legacy 6MT, N/A, with 130k. Just bought it a couple months ago. A few weeks ago it began making a weird grinding noise only on throttle. Still felt fine to drive though. Then it suddenly developed an odd thumping coming from the wheels on tight turns. My research would indicate this is the center diff gone bad. It has now started thumping continually and significantly worse. It feels sort of like the wheels bind momentarily and then pop back somehow. Took it to the shop and they've said the transmission may need fairly extensive (and expensive) repair. They are working on getting a price quote for me but I am expecting the bill to be in the thousands for sure. ALL THAT just to say, in the event the bill to rebuild is insane, I would much prefer to just drop the old transmission and put in a used one, but can't find any used ones available for a 2012 Legacy. My main question(s): will any of the previous year Subaru Legacy 6MT bolt up and run fine with my 2012? Does anyone have firsthand experience replacing a 5th gen's transmission with a different year or know where I can look to check compatibility? Will the transmission from a different make bolt up to the 2012 legacy, such as a Crosstrek 6MT? Couple things I have gathered so far (please correct if I'm wrong and I will update): The GT's and Outbacks have slightly taller gears than the normal Legacy. A transmission with a different gear ratio than mine can still potentially be used as a replacement, so long as the matching rear differential is also swapped in. The part numbers for transmissions throughout the years are different (but does this guarantee that they cannot be swapped?). Thanks in advance everyone! I hate asking the "will this fit my _____????" questions but I've done as much searching as I know to do, so I figured I would make a proper thread. It may be helpful to others down the line as well! Thank you! Edited December 5, 2021 by Tooth_Brush Link to comment Share on other sites More sharing options...
Fabsx Posted December 4, 2021 Share Posted December 4, 2021 Replaced my moms 2010 legacy 2.5 6mt with a 2012 legacy 2.5 6mt. Drove good for the two years after replacement before it was totaled. Not to mention, upgrade the shifter bushing/plate and what not while it was out. Buddy also did his 2010 Legacy GT with a 2011 legacy sohc 6mt with no issues and running 4+ years. So I would say they are interchangeable. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
DrD123 Posted December 4, 2021 Share Posted December 4, 2021 I think the only difference is that 5th and 6th are a little taller on the GT than the NA engine cars - final drive is the same, so they should work just fine. I'd actually like a shorter 5th... Link to comment Share on other sites More sharing options...
Tooth_Brush Posted December 5, 2021 Author Share Posted December 5, 2021 (edited) Replaced my moms 2010 legacy 2.5 6mt with a 2012 legacy 2.5 6mt. Drove good for the two years after replacement before it was totaled. Not to mention, upgrade the shifter bushing/plate and what not while it was out. Buddy also did his 2010 Legacy GT with a 2011 legacy sohc 6mt with no issues and running 4+ years. So I would say they are interchangeable. That's great news! 2010 and 2011 Legacy transmissions are a plug and play install into the 2012. That's super encouraging to hear that. Thank you for sharing your experience! Is there any reason you might think 2013-2014 Legacy transmission wouldn't fit? I would also like to replace/upgrade shifter bushings while it's out. Any chance you remember what shifter plate you used to upgrade? I've heard some good things about the Boomba short shift plate. I think the only difference is that 5th and 6th are a little taller on the GT than the NA engine cars - final drive is the same, so they should work just fine. I'd actually like a shorter 5th... Ah, thank you. I updated my original post to reflect that. Would you still have to swap in the rear differential with just taller gears or would that be unecessary? I am a bit of a transmission noob so I am learning a lot here. Thank you so much guys! Can't tell you how much I appreciate it. Edited December 5, 2021 by Tooth_Brush Link to comment Share on other sites More sharing options...
DrD123 Posted December 5, 2021 Share Posted December 5, 2021 I don't think you'd need to swap anything out - the transmission should swap over as a unit, I think. (as long as it's a Legacy transmission, and not an Outback) Link to comment Share on other sites More sharing options...
dgoodhue Posted December 6, 2021 Share Posted December 6, 2021 I would check your tires to make sure the tire depths are even. Usually the center differential going out is because someone replaced 2 tires instead of all 4 or a tire was damaged and they installed one new tire. Link to comment Share on other sites More sharing options...
Tooth_Brush Posted December 9, 2021 Author Share Posted December 9, 2021 (edited) I don't think you'd need to swap anything out - the transmission should swap over as a unit, I think. (as long as it's a Legacy transmission, and not an Outback) Thanks for that image! That is super helpful. Am I right in assuming these specs are for all 5th gen Legacy years, correct? Sorry for my ignorance here. Thank you! Edited December 9, 2021 by Tooth_Brush Link to comment Share on other sites More sharing options...
Tooth_Brush Posted December 9, 2021 Author Share Posted December 9, 2021 I would check your tires to make sure the tire depths are even. Usually the center differential going out is because someone replaced 2 tires instead of all 4 or a tire was damaged and they installed one new tire. Thanks for the suggestion!! Tires look good and were new when I bought the car. My guess is that the previous owner towed it incorrectly or did something like what you described with the tires at some point. A real shame. Car appears to be pretty well taken care of otherwise :'-( Link to comment Share on other sites More sharing options...
DrD123 Posted December 10, 2021 Share Posted December 10, 2021 Thanks for that image! That is super helpful. Am I right in assuming these specs are for all 5th gen Legacy years, correct? Sorry for my ignorance here. Thank you! Correct - 2010-2014 Legacy Link to comment Share on other sites More sharing options...
Tooth_Brush Posted December 10, 2021 Author Share Posted December 10, 2021 Correct - 2010-2014 Legacy Thank you for all your help! If I could ask one final question that you may know -- will the wiring from 2013-2014 transmissions work in our 2010-2012 cars? I understand Subaru switched from EJ to FB motors in 13-14 and everyone says how the CANBUS in these cars is very picky. I would hate for everything to bolt up perfectly and then have the electronics freak out lol Should just be a couple harnesses on the tranny so I'm not super worried, but if you have any thoughts I'd like to hear! Seriously thank you so much! Link to comment Share on other sites More sharing options...
dgoodhue Posted December 13, 2021 Share Posted December 13, 2021 Thank you for all your help! If I could ask one final question that you may know -- will the wiring from 2013-2014 transmissions work in our 2010-2012 cars? I understand Subaru switched from EJ to FB motors in 13-14 and everyone says how the CANBUS in these cars is very picky. I would hate for everything to bolt up perfectly and then have the electronics freak out lol Should just be a couple harnesses on the tranny so I'm not super worried, but if you have any thoughts I'd like to hear! Seriously thank you so much! In looking at the service manual, I think the 6MT models only has 2 sensors, one for the neutral and one for reverse. In looking at the online parts interchange those parts are interchangeable. Link to comment Share on other sites More sharing options...
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