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Transmission Center Differential Upgrade


Marcazi

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Well, here we go again. Last year in late December, I had just gotten my transmission back from a great shop on the east coast with a brand new center differential, output shaft, a few bearings, and some seals after 77 miles on the car. Now, 32k miles later, 15+ autocrosses, and a few drag strip runs, my tranmission is making the same noise. I had learned the hard way previously about donuts, wrong size tires, and the like, so I do take it easy on the car. I also needed a clutch at the time, but could not afford to put a new one in at the time, so I just put the stock one back in. The stock clutch is still in working condition at this point, but I will be replacing it this time around.

 

I have since pulled the transmisison, and am totally stuck at what to do. The shop that worked on it previously was more than happy to look at it again, and replace anything that they might have screwed up with reassembly, or something that they did. Unfortunatly, I am having trouble finding shipping for less than $400 round trip out there again, and Im not wanting to drop so much on the shipping again!

 

I was told by a few that the center differential is fairly easy to pull out and inspect, and I would be able to replace some bearings myself if that is infact the issue.

 

I also now have a local in my autocross region that has worked on a few friends subaru transmissions and owns a reputable shop in the area, that I would assume could rebuild whatever I needed to OEM spec.

 

So, the questions I have.... Do I send it away? Look at it myself? rebuild to spec? Upgrade to a better diff? if so, which ones?

 

I plan on autocrossing a full season, a couple full track days, a few rallycrosses this winter, and some more strip time. I still want a comfortable daily/vacation car, a not a full track car.

 

Here is what I have for driveline upgrades

 

2005 GT Wagon, 5MT

Stage 2

Whiteline Front control arm bushings

Whiteline Lower Controla arm busings

Group N tranny mount

Group N rear shifter bushing

Group N X member bushings

Sti Short throw shifter

Spt Front frame brace

AVO rear frame brace

BC Coilovers

Kartboy Endlinks

Hotchkis front and rear sway

AVO rear sway mounts

Whiteline rear diff busings

Hankook Rs-3 225s 17s

 

 

Thanks for all the help!

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What shop was doing the work?

 

$400 is too much for shipping. The shop that does the work might be able to set up a call-tag for shipping, and get you a bit of a discount.

 

There are really no options for upgraded center differentials, unfortunately. You are stuck with what you have, unless you want to "upgrade" and reduce the performance of the car (by going with a stiffer STi center diff, really only good for rally use or drag use, or the Cusco tarmac diff, which is an open diff).

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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Ahh, I thought it was $400 each way. I missed the "round trip" part.

 

I'd send it back and let them take a look. They are the best Subaru trans. shop in the country for a reason.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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Hard to say. Lunching does a number on the center diff, but in just 30k miles, that seems odd.

 

What noise is it making? It could be something like transfer bearings.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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PPG makes an upgraded torsen center for the 5mt. $2k+ though.

 

Not readily available. I've driven one, though, and it is sweet. I drove a car that had all 3 of their diffs. Gripped like a boss.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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Yes, all this happening in 30k miles was puzzling. All of this on the stock clutch too, and I never ever launched it. The noise is constant, just like what happened before, in any gear, under slight accel or decell. The output shaft does seem to wiggle a bit more than it should, but I'm no expert. The last time, it started to make noise and I didn't think much of it, it got worse and I thought the damage had already been done. This probably caused the output shaft and a few more things needing to be replaced.
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I'd be surprised if it wasn't the transfer bearings.
[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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Well, It was finally picked up by a shipping company today, off to Andrewtech. :) Hopefully it is minimal so I can possibly upgrade to a LSD instead, I guess I will wait to find out. What else can I upgrade to help this last? I use Subaru Extra-S, and change it more than factory.........
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Well, It was finally picked up by a shipping company today, off to Andrewtech. :) Hopefully it is minimal so I can possibly upgrade to a LSD instead, I guess I will wait to find out. What else can I upgrade to help this last? I use Subaru Extra-S, and change it more than factory.........

 

Extra-S helps and a frequent change interval. Really it is 90% how you drive it, those guys that beat on their gearboxes break em ;)

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  • 3 weeks later...
As we suspected, it was the transfer bearings. They said that they put different ones in than they took out, looks to be Subaru made some changes to make them better. 3 new bearings and a clutch and I am good to go.
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Good thing you caught it before they let go and took out the rest of the gearbox.
[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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  • 8 months later...

That sucks, sorry to here. Ever think of doing a STi 6MT swap. The gearing isn't the best for drag strip. But it's the strongest trans axle Subaru makes. I swap mine back in 07. Just drop it out to put new clutch set in with 100k on the old set. The clutch had a little life in it, but the TOB was making noise.

 

I have over 207k on my LGT & 165k ( Bought used at 30k + 135k, I put on it.) on the STi 6MT.

Mileage:331487 Retired/Sold

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Im not convinced that the swap is the answer for me. I would love a stronger box, and might as well do a brake upgrade at the same time, but I won't be happy with the gearing, I'd really like to stay with the 5 speed. Transmission is out today with it heading to a friend at a dealer for a teardown tomorrow.
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  • 2 weeks later...
Any updates on this? I have 130K and my center diff just started screaming. It looks like I can remove it without removing the trans.

 

You can pull the rear section without dropping the trans, yes.

[URL="http://legacygt.com/forums/showthread.php/proper-flip-key-interesti-159894.html"]Flip Key Development Thread[/URL] "Genius may have its limitations, but stupidity is not thus handicapped." - E. Hubbard
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