STI trans fitted into 5th Gen LGT

You have my attention...

Are you sure the rear end wasn't from a 2010 2.5i CVT Outback? The Legacy has a 3.70:1 ratio, the Outback has a 3.90:1 ratio which matches the rear gear ratio of a 2015 STI.

 

To throw a bit of a wrench in this, I keep finding that the rear end ratio for the 2007+ STI is 3.54 because of the 1.1:1 output gear, while the front ratio is 3.90.

 

Edit- in looking into this further 07-14 sti uses a 3.54 rear diff, 2015+ uses a 3.90 rear diff. Be careful what you buy!

Edited December 15, 2019 by FLlegacy

That is what the shop told me.

The shop that did the conversion is TDC, Top Dead Center Motorsports in Bradenton, FL. jttdcmotorsports@gmail.com

This is confusing to me too. Subaru's parts website shows 3.545 in 2015+ as well. As seen here. Flatironstuning shows 2007-2018 STI rear ends also being 3.545 here. It seems like we would need to swap to an earlier model WRX R160 to get the proper 3.545 rear end with a modern STI transmission using 1.1:1 transfer gears. Or use an older transmission with 1:1 transfer gear and find a 3.90 rear end.

Hrmm it's weird too. The part number for just the pinion that I linked above shows G/R 3.545 but the full part number for the entire diff 27011AB320 shows 3.90. I am having major trouble finding/verifying the transfer reduction gear of the 2015+ sti. The shop that specializes in this kind of stuff is probably right, though.

This is confusing to me too. Subaru's parts website shows 3.545 in 2015+ as well. As seen here. Flatironstuning shows 2007-2018 STI rear ends also being 3.545 here. It seems like we would need to swap to an earlier model WRX R160 to get the proper 3.545 rear end with a modern STI transmission using 1.1:1 transfer gears. Or use an older transmission with 1:1 transfer gear and find a 3.90 rear end.

 

The 2015 sti dif ratio was verified to me by the owner of subieautoparts.com they strip and sell STI's and WRXs. I trust him to know what he is selling.

 

If someone was so inclined it might be easier to source the 1:1 transfer gears and swap them into the 07-14 sti trans. It should be a straight forward swap.

I forwarded the posting to the shop, if they have any comments.

Just about to complete the installation of an STI 6 speed into my 2010 LGT mt. Had custom engine mounts created to handle the conversion to the STI 6 speed. No custom parts other than the mounts. The rest of the parts came from different yr and model Subaru's. Checking to see how much interest would be there if I offered these mounts for sale.

Very interested. I already have the trans and R180 from a 2016 STI when it's time.

 

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Just found out that the shop had sent me an updated message a while back correcting the diff identification. I did not get the update. They are re-sending the info for the diff used.

Here is the message that I missed from the shop. We used the rear diff from an 04 wrx we had at the shop, it was going to be the 2010 legacy rear end and change the transfer gears since the 3.90 rear diff is more available.

Here is the message that I missed from the shop. We used the rear diff from an 04 wrx we had at the shop, it was going to be the 2010 legacy rear end and change the transfer gears since the 3.90 rear diff is more available.

 

So it is a 3.54 ratio rear diff then. Thank you for the clarification.

Any updates on this? Are you driving it around yet? How much are the mounts?

 

 

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I am driving the car. Trans works well. Ratio's are different than the oem GT trans. I am waiting for a quote on the mounts.

Do you have any pics of how it mounts to the trans? And what axles are you using?

 

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Do you have any pics of how it mounts to the trans? And what axles are you using?

 

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His shop reused his OEM axles with a 3.54 wrx rear diff. It bolts right in to our cars and is fairly easy to find used.

 

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The engine mounts were custom made. Waiting for a price. They will be offered for sale.

The engine mounts were custom made. Waiting for a price. They will be offered for sale.

Thanks Gary. Looking forward to getting another piece of the puzzle.

 

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Definitely interested in this as well

Did this go anywhere? I'm also interested.

They will be $800 shipped to the continental U.S.

Just waiting for the insurance agent to get back to the seller re: coverage.

They will be $800 shipped to the continental U.S.

Just waiting for the insurance agent to get back to the seller re: coverage.

 

Are these mounts that go on the transmission or mounts that hold the engine to the chassis? I have seen it done both ways.

They will be $800 shipped to the continental U.S.

Just waiting for the insurance agent to get back to the seller re: coverage.

 

Woof. I doubt there will be at lot of takers at that price.

Woof. I doubt there will be at lot of takers at that price.

What do yo mean, it's only 2x the cost of the blast plates, plus the STi trans and all the incidental bits.

It's not cheap, but if everything else for the swap is just stock parts other than possibly the shifter, you will still majorly cut down on the widely-accepted 10k price for a complete conversion.