I've searched up and down to no avail for any type of documentation (aside from the FSM) on tearing down the STI 6 speed transmission so I decided to put something together as a reference for anyone looking. After shredding 2nd gear in my transmission I've been motivated to trying to get the gear stacks out of the transmission myself, mainly to save on labor costs on the rebuild. This is not a fully inclusive how-to, but covers everything involved in removing the case and gear stacks. Hopefully it will be useful to someone! I didn't document anything having to do with removing the transmission from the vehicle - it would be my assumption if you're looking to tackle this yourself, you're mechanically savvy enough to have gotten that far... I didn't document my steps on removing the tail housing of the transmission, but IAG's instructions for transfer gear installation is a great reference (first 4 pages)... https://www.iagperformance.com/v/vs...1000/IAG-Transfer-Gears-IAG-DRV-1000-1010.pdf That leads me to this point. The trans is on the table and the tail housing and output shaft have been removed... Note that this specific transmission is from an '07 STI and should be similar to 08+ STI. 04-06 are slightly different in that they still utilized an oil pump. I set the case on a couple of 2x4's so there is clearance for the input shaft underneath (it protrudes from the transmission bellhousing about an inch). Disconnect the diff electrical plug Now the diff will just slide right off of the pinion shaft. There are 4 of these clamshell bearings that go between the diff and the pinion shaft You should now see this view (pinion shaft with diff removed pictured top (sleeping doggo optional)) Side view Remove this roll pin Roll pin removed Remove snap ring and washer Pull up to slide the spring out. Careful because it will snap shut and could pinch your finger! Next, on the side of the case remove this bolt, spring and ball (top center of picture, partially backed out) With that removed, these will both pop out together You should be left with a view similar to this cont...
Remove all of the torx (size 40) bolts holding the oil pump block plate onto the housing. (Note: this transmission is out of a late '07 STi so it no longer has the trans oil pump. This section will be slightly different for 04-06 STi transmissions. Please refer to the FSM for any missing steps here) Pump block plate removed Remove the spacer and snap ring from the main gear stack Next remove the 3 spacers from the pinion shaft Current view with snap ring and spacers removed Remove these two bolts from the side of the case And this one (center of pic and partially backed out) Remove all of the bolts holding the case on Don't forget the 3 nuts that are under the oil pan With a little persuasion to loosen the RTV, the case should easily slide right off (do not force it) Lots of spin-a-ma-things going on in here Cont...
Push the center shift fork up to shift the trans into 4th gear This allows room to remove the reverse idler holder Next remove the 3 plugs and springs that hold the shift fork shafts in And remove this one that holds the reverse gear shaft in At this point you are ready to pull the gear stacks out. They have to come out with the shift forks and reverse gear all simultaneously. An extra hand would be very helpful. I ended up laying the trans on it's side so I could pull everything out at the same time by myself. Gear stacks out The shift forks will just come right off the stacks What you're left with And there you have it - gear stacks are out. My plan is to take the gear stacks to my favorite Subaru performance shop so they can swap the gears out. My understanding is that you need to setup a jig of sorts in a press to be able to get the stacks disassembled - I'll leave that for the pros. Side note: 1st and 2nd drive gears are part of the input shaft, so in my case I'll be needing a new input shaft in order to replace the shredded 2nd gear (as well as a new 2nd gear driven gear) Reassemble in reverse order Hopefully this is somewhat helpful. If you have to go into the trans further than this to get to the front diff, you're on your own unfortunately. Feel free to post any questions/comments!
