i read an article somewhere, let me see if i can find it.

 

I just realized the spec b is kinda hard to find lol. so what about the new 2010 transmission? I should be able to find a wrecked on sometime durring winter...

 

i want a 6 speed for the same reason. I hate how i can get close to 30 doing 65 but then i go up to 70 and its falls to 25 something!

 

A 6-speed wont help your gas mileage or drop RPM's. Everyone that I've seen the ratio in sixth is the same as our fifth, its just shorter 1-5.

 

A 6-speed wont help your gas mileage or drop RPM's.

In fact, a 6-speed won't help your gas mileage even if it did drop your RPMs. Fuel efficiency is dependent on two factors: how much fuel is used during a period of time and how far you go during that exact same time. It took me a long time to come to terms with this, but fuel consumption in a fuel-injected car is not dependent on how fast your engine is spinning, but actually on how much work it has to do to keep spinning (or change its speed). The reason your fuel economy drops so dramatically from 30 mpg to 25 mpg as your speed climbs from 60 mph to 70 mph is because there is dramatically more wind resistance on the car due to its higher speed. So, your engine has to burn more fuel to maintain pace.

 

There is a lot to look into for a 6-speed swap. You can do just the trans or also swap in the R180 (Spec B and STI) rear diff in place of our R160, or go all out with STI axles and 5x114.3 hubs.

This thread is useful(http://legacygt.com/forums/showthread.php/6mt-master-swap-thread-107137.html?t=107137), though Legacy specific, just remember that our cars are 3.9 final drive like the 2007-09 Legacies. Looking at the ratios on cars101.com it looks like the Spec B has a bit lower 6th than our 5th.

All the STIs had shorter 6th than our 5th. The trans that is easy to swap in unless changing final drive ratios is the 04-05 since they use 3.9 (later years use a stepper gear and 3.454 rear diff). But your gearing will be shorter, and changing that via gear swaps or final drive swap is much more involved. Info for all that and more over on NASIOC http://forums.nasioc.com/forums/showthread.php?t=187454

The '10 Legacy 6 speed does have quite a bit taller 6th, no idea of that bolts in, but could as it is based on the 5-spd.

Personally I think the 6spd swap is only worth it if you are using an STI trans to get the DCCD and front LSD, the Spec B has the same strong 6-spd, but open front diff and viscous center. But the Spec B has the taller 6th and the right 3.9 final drive you need.

 

yeah dude, don't do a six speed swap for the mpgs. i dont think you'll ever make up the defecit from the costs associated with procuring and getting the swap done vs what you think you'll save in less gas being used.

and further, i'm down about an average 3 mpg over the course of two months since my six speed swap. do it for the performance, reliability, and dccd as power6 said and you'll really love your results! and now that it's been done and documented it really isn't that hard for others. g'luck!