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Replacing Synchros DIY Anyone?

('06-'08) 
12K views 18 replies 8 participants last post by  el Fox beSTIal 
#1 · (Edited)
2nd will not get into gear after quick high rpms upshifts (Drag Strip) and 3th to 4th grinds so I have decided to replace the synchros myself.

I have tools, press, garage, Service Manual and I am mechanically inclined and tend to be successful in everything I have attempted on the Foz so far, asking for guidance or suggestions on how to accomplish replacing the synchros set.

Also, wondering since I plan to attack the strip on a weekly basis, is there an upgraded more robust synchros set?

I do not want to go 6MT just yet, the added weight does not appeal to me and gears are ok, I know how to shift it is just synchros have 100K miles.

Cocktails are an urban myth, tried that already, and I do not believe in built 5MTs either, they seem to last only a few thousand miles.

I am not afraid of failing as that will be a direct path to a 6MT.
 
#2 ·
woah hold up there partner.


Have you confirmed that its not a clutch issue first, before you go ripping into your trans?

Having trouble getting into multiple gears sometimes points to a clutch pressure plate issue, perhaps a warped spline, that isnt letting the clutch disengage fully... or even needing a good clutch bleed (low pressure). Did these gears all of a sudden start giving you trouble, or did they slowly pop up one by one?

Does the car have trouble getting into 1st at a standstill? How about 5th to 4th downshifts at highway speeds?
 
#5 · (Edited)
woah hold up there partner.

Have you confirmed that its not a clutch issue first, before you go ripping into your trans?

Having trouble getting into multiple gears sometimes points to a clutch pressure plate issue, perhaps a warped spline, that isnt letting the clutch disengage fully... or even needing a good clutch bleed (low pressure). Did these gears all of a sudden start giving you trouble, or did they slowly pop up one by one?

Does the car have trouble getting into 1st at a standstill? How about 5th to 4th downshifts at highway speeds?
Haha, ok I will stop my skinny fingers from busting open the trans...per your suggestion, I will try first to slow bleed the clutch, then if that does not do it will separate the trans from engine and try to inspect for bent splines assuming the 5" gap between bell housing and engine is sufficient to inspect the splines.

I replaced the clutch 4K miles ago, Stage 1 Exedy and new OEM pilot and sliding bearings and no issues for 4K miles until I started dragstrip duty, first the sliding bearing started whining and quiets upon slightly depressing the clutch, it is not a cold morning whine, whines all the time so long the clutch is not depressed. A couple weeks after the bearing whine surfaced, I started having issues not succeeding in high rpm fast 1st to 2nd upshifts. As far as the 3th to 4th grind IIRC I had it for a while prior to clutch replacement but rarely surfaced as I was not hitting the strip at the time.

Car does NOT have trouble getting into 1st at a standstill, and NO issues on 5th to 4th downshifts at highway speeds, the only issues I have is not been able to engage 2nd during high rpm 1st to 2nd upshifts getting out of the hole at the strip, and a grind during +5K rpm 3th to 4th upshifts. During normal driving tranny shifts smoothly, no grinds and 1st to 2nd no problem.
 
#9 · (Edited)
Before ripping this thing open, may i suggest one last test.


Uncle scottys cocktail

-1 quart synchromesh
-1 quart redline lightweight shockproof
-2 quarts castrol Hypo C gear oil ( or any 75w-90 manual gear oil)



Sounds like a trans issue to me now that you've discussed it a bit more. My stock 5spd back when it was stock grinded all gears BAD, esp on cold mornings. The cocktail solved everything instantly for me. Perhaps it can buy yourself enough time to collect a 6spd swap. If you do an 04 STi 6spd you will only need 3 main things...

-04 STi trans (and shift linkage)
- your year AUTO forester driveshaft
- 02-05 WRX rear diff (3.90 ratio)

Dont forget things like a DCCDpro controller (manual or auto) . you CAN use the 5spd crossmember too... ask me how i know lol.
 
#18 · (Edited)
If you do an 04 STi 6spd you will only need 3 main things...

-04 STi trans (and shift linkage)
- your year AUTO forester driveshaft
- 02-05 WRX rear diff (3.90 ratio)

Dont forget things like a DCCDpro controller (manual or auto) . you CAN use the 5spd crossmember too... ask me how i know lol.
Front axles are different 04 STi vs 07 FXT, I would need these too.
For R180 04 STi rear diff can I use the 07 FXT rear axles?
Will the 5MT 07 FXT driveshaft work with the R180 and 6MT 04 STi.

http://i139.photobucket.com/albums/q307/Boost_Addict/IMG2783.jpg
 
#10 · (Edited)
^Replaced fresh (4k miles) Extra-S with 1qt Penzoil Syncromesh and 3qt Valvoline dino, did not work, just wasted $100 of Extra-S :(

If I go 07 STi I would add to the list hybrid front axles, right? Brand new 6MT 07 STi trans can be had for approx $4,000 plus shipping.

However, my gears are still intact so I would rather fix the 5MT until it explodes.
 
#11 · (Edited)
where did you pay $100 for the extra-s? how many quarts? i got my 4 qts + 1 qt syncro magic for $75, shipped.

i started with the smurf blood regimine several times that didn't quite help. then i went on to uncle scotty's cocktail mix several times that helped. the more miles i had added, it didn't seem to work as well. then when i tried the syncro magic and then the extra-s (couldn't get into first or second), it helped a bit. but about after a month, things were gradually feeling much better. it became like butter. lasted me another year till tranny finally failed.

all this was ever since i've had the car. but i'd have to say the extra-s has given me the best results so far.

(Sent from my Android via Tapatalk)
 
#16 ·
i get my stuff from here:

http://www.rs25.com/forums/showthread.php?t=118882

the synchro magic is poured into the existing fluid, driven for about a half hour and quickly drained. then you add the 3.8(?) qts of extra-s. it's supposed to help with grinding issues but i took a chance to see if it would help with my issues of not being able to get into 1st and 2nd. well, almost impossible. in about a few weeks, it worked and shifted really smooth. gave me another year with my failing tranny till it finally croaked.

(Sent from my Android via Tapatalk)
 
#17 ·
ahh crap missed the part about already trying cocktails , dropped the ball on that one.

Welp, it sounds like the synchros are just that shot at this point. If you did an 07 STi swap, you would need to do hybrid fronts, and im not sure about the rear because the 05+ years required the specific STi axles which only fit the rear 5x114 Brembo hubs.

I mean if doing a 4 hub swap to brembos AND sti trans/rear diff is in your budget, then by all means go for it. When swap time came, that would have tacked another easy $1500 or so on for me, so i decided to do WRX sized with an 04 setup... made everything simple and i am happy with how powerful the brakes still are.
 
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