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Old 05-21-2017, 07:44 PM   #1
Juice66
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Default Rebuilt STI 6 speed issue

Finished rebuilding an STI 6 speed but after installation of transmission, I'm having a strange issue. Tore down transmission due to 4th popping out of gear and the typical synchro grind for a 2004 STI. This is not my first 6 speed rebuild but it is my first time having an issue. Replaced 1-6 synchros, 3/4 sleeve and hub assembly, 4th gear, 3/4 and 5/6 fork. I'm unable to get into 5th gear from 4th but once in 5th, I can easily go into 6th and back to 5th. The front shifter stay pushing is original with a lot of movement during gear change. I never drove this car prior to repair but everything is installed per subaru repair manual with use of all oem tools. It seems like a sort of bind from 4th to 5th. Any help is greatly appreciated before I remove it and tear it down.
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Old 05-22-2017, 12:33 AM   #2
mrsaturn7085
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The shiny metal ring between your 6th gear synchro and 6th gear makes me think you may be mixing up a bushing in this area - this gap is not normally present and will affect shift engagement of 5th/6th. Verify the 5th and 6th gear bushings are correct and are in the correct positions. 4th gear bushing is physically very different so it shouldn't be a problem. If these look good (I don't think they can be flipped), you might make sure you have the gear stack pressed far enough down the shaft...?

Your outer hub rings are both correctly oriented on the input shaft, but you might verify the direction of the inner hubs. Off the top of my head, I know these can be installed backwards but I'm not sure if you can fully reassemble the shaft without fixing this.

Did you re-measure and re-size the input shaft snap ring and preload washer after replacing the parts on the two shafts?

Last edited by mrsaturn7085; 05-22-2017 at 12:48 AM.
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Old 05-22-2017, 12:52 AM   #3
Juice66
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I can assure you not one thing was left out. That gap is normal. The baulk rings actually jingle in their respective locations when not engaged to the gears dogs. Not one thing was over/under looked. I'm considering possibly a reverse lockout issue with the cable or other. I'm not convinced It's internal but I just hope it's not.
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Old 05-22-2017, 01:17 AM   #4
Juice66
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Default Rebuilt STI 6 speed issue


All three bushings installed per subaru specs and oil holes offset to mainshaft oil hole.
I did not measure because it's not necessary unless replacing main shaft or case, in my experience. As this isn't an appropriate answer, I don't know of any professional shop, including the ones well known for 6 speed rebuilds, that take transmission measurements aside from pinion depth, front diff preload/backlash or possibly transfer gear snap washer clearance
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Old 05-22-2017, 01:17 AM   #5
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EDIT: You're right - I have a freshly pulled mainshaft sitting on the floor of my garage and was referencing it, but the synchro was hanging up when I tried to move it. Gave it a little more push and it slid free enough to leave a gap like the image you've shown.

What do the actuators on your blocker shaft look like?
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Old 05-22-2017, 01:31 AM   #6
Juice66
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I should've taken more pictures for this rebuild like i did my first but the interlocks were orientated the only they can be set in order for you to install both interlock pilot bolts.
Picture is dark but interlocks positioned this way.
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Old 05-22-2017, 12:39 PM   #7
mrsaturn7085
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Your front interlock block is upside down - the notch near the roll-pin in the image should be facing rearward. This *may* affect shift gating - hard to say. If installed backwards, it will still allow the pilot bolts to be installed. Your rear interlock block (reverse) is installed correctly.


Last edited by mrsaturn7085; 05-22-2017 at 12:46 PM.
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Old 05-22-2017, 01:34 PM   #8
Juice66
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Quote:
Originally Posted by mrsaturn7085 View Post
Your front interlock block is upside down - the notch near the roll-pin in the image should be facing rearward. This *may* affect shift gating - hard to say. If installed backwards, it will still allow the pilot bolts to be installed. Your rear interlock block (reverse) is installed correctly.



That picture with the interlocks is a different transmission. I took that picture right after removing the main case during teardown.
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Old 05-22-2017, 02:30 PM   #9
mrsaturn7085
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I don't know what to tell you, because that image comes directly from the 2006 FSM. It is repeated on page 6MT-114 explicitly stating 'Make sure to install the reverse interlock block and interlock block in proper direction.'

The image you linked is clearly backwards... but whether or not that matters is hard to say (not sure if the teeth are symmetrical or not). If both transmissions have that part oriented like the image you linked, then they are both backwards. I'll take a look at the spare parts I have over my lunch hour today.
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Old 05-22-2017, 03:19 PM   #10
Juice66
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Quote:
Originally Posted by mrsaturn7085 View Post
I don't know what to tell you, because that image comes directly from the 2006 FSM. It is repeated on page 6MT-114 explicitly stating 'Make sure to install the reverse interlock block and interlock block in proper direction.'

The image you linked is clearly backwards... but whether or not that matters is hard to say (not sure if the teeth are symmetrical or not). If both transmissions have that part oriented like the image you linked, then they are both backwards. I'll take a look at the spare parts I have over my lunch hour today.


That picture was from an 08 or 09 sti and i can assure you it shifted and drove as designed after the repair. I simply removed the interlock rod from its original orientation from when it was installed in japan in 2003 on this one I just did.
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Old 05-22-2017, 04:13 PM   #11
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Yep, looks like the 2006 shaft I pulled is oriented the same way. I'm stumped - good luck figuring it out!
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Old 05-22-2017, 04:23 PM   #12
Juice66
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Quote:
Originally Posted by mrsaturn7085 View Post
Yep, looks like the 2006 shaft I pulled is oriented the same way. I'm stumped - good luck figuring it out!


I appreciate it. This isn't a DIY friendly repair, so not many people will have the experience you have. Fortunately I have access to all the appropriate tools to do the job. It's definitely bothering me though and I sure as hell don't want to tear it down again.
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Old 05-22-2017, 05:26 PM   #13
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I don't know if you've been following my dogbox build thread, but I hear you on that one... I really do.
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Old 05-22-2017, 05:40 PM   #14
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I haven't read every post but I've looked at quite a bit
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Old 05-22-2017, 06:06 PM   #15
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Completed the rebuild, installed the transmission, heard some odd noises, pulled the whole thing out again, and found a bent input shaft. It's completely torn down a second time, currently.
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Old 05-22-2017, 07:11 PM   #16
Juice66
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The main shaft?!?!?!
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Old 05-22-2017, 10:35 PM   #17
mrsaturn7085
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Yeah, the input shaft (layshaft). The Hewland part is thoroughly trimmed to save weight, but it's still a 3/4" piece of billet steel that was bent. Hardened to 60 Rockwell, too. I've already shipped the shaft back to the UK to have the gears swapped to a good shaft.
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