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Premium Member
2007 XT Sport 5MT
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24,015 Posts
Discussion Starter #1 (Edited)
I was doing some miscellaneous gear ratio calculations and though I would double check some numbers.
Based on the info I found pertaining to the 6MT from the MY10 Legacy and Legacy GT on cars101.com there could be a cheaper alternative to the Spec-B "fuel saver" 6MT swap.

The MY10 ratios are as follows:
1st - 3.454
2nd - 1.947
3rd - 1.247
4th - 0.972
5th - 0.782
6th - 0.666

Final - 4.111 <- this factor here made me realise you could run this setup simply by swapping to the FXT 4EAT rear diff (4.111) and if the new 6MT is anything like the STi 6MT in length, you could also use the 4EAT driveshaft.

By not having to swap out rear diffs to make the Spec.B's 3.454 Final Drive work in our FXT's... you could save by just picking up the parts from a 4EAT Forester instead.

Calculating based off my 245/40-18 BFG's I estimate that it would be a 2% drop @75mph in 5th gear compared to my current 5MT FXT, but the added 6th gear would drop those RPMs by 17% over my 5MT to make for a pretty decent cruising gear for the highway.
Albeit the Spec.B would give you more significant RPM drops (6% and 26% respectively) but might set you back more if you have to swap to the Spec.B's R180 rear diff as well as the appropriate rear axles to make that combination work.


Just thought I'd throw the idea out there, feedback if more than welcome...
a 6MT swap on my FXT is just a pipe dream at the moment with my other project eating up all my free cash.

Anybody?
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
I wouldn't waste my time. The new 6MT is, essentially a 5MT with an extra gear on the back of 5th.

Don't expect strength gains, and swapping the whole assembly is going to be a PITA. NOT a straight forward swap like the round-case 6MT.
 

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Premium Member
2007 XT Sport 5MT
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24,015 Posts
Discussion Starter #5
I was unaware it was completely different, it was really more of a random idea than anything else.
I don't suspect my FXT will need a transmission much if at all stronger than my current 5MT though.
 

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Premium Member
07 Forester XT
Joined
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6,759 Posts
I wouldn't waste my time. The new 6MT is, essentially a 5MT with an extra gear on the back of 5th.

Don't expect strength gains, and swapping the whole assembly is going to be a PITA. NOT a straight forward swap like the round-case 6MT.
I was gonna say.... Yeah shame they cheaped on it but it also keeps the costs down.
 

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Premium Member
2009 Outback XT-B 5MT
Joined
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10,254 Posts
It's a completely different trans than the STI trans. It is constructed almost exactly like the 5MT, with gear widths not much (if any) wider.
 

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Premium Member
2007 XT Sport 5MT
Joined
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24,015 Posts
Discussion Starter #9 (Edited)
Props for thinking outside of the box. But are we really after fuel saving here?
Yeah, I was really just thinking of dropping my fuel consumption on long highway road trips. I've got a fuel economy tune that is only really effective below 3000RPM which means it's not much use at the typical Canadian highway cruising speeds (~3200RPM)

It's a completely different trans than the STI trans. It is constructed almost exactly like the 5MT, with gear widths not much (if any) wider.
Oh well, it was worth a shot...
I was just looking for an "overdrive" option to get my revs down at highway speeds.
 
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