The Subaru SVX World Network

The Subaru SVX World Network (https://www.subaru-svx.net/forum/index.php)

- Transmission and Drivetrain (https://www.subaru-svx.net/forum/forumdisplay.php?f=67)

- - Spec B swap (https://www.subaru-svx.net/forum/showthread.php?t=61714)

So, after doing some digging, ive run into the idea of using the tranny from the 07 and later Legacy Spec B. They are 6 spd with gear ratios closer to our factory trannies. The final drive ratios look more to par with our factory setup as well. Has anyone else looked into this for a swap option, or am i completely off my rocker?

been looked at...it all comes down to how much $$ you've got to spend.

Bill

Solid answers here...

The 07&08 Spec B tranny would be a great swap for the SVX if you are OK with not having some of the 6MT features. The Spec B DOES NOT have a front LSD or DCCD.

The Spec B tranny would allow you to use the SVX rear R160 diff. It is a 3.9 final drive however it has a 1.1:1 center diff which allows the use of the 3.54 SVX rear diff. You will also be able to use the SVX auto driveshaft with the Spec B tranny. And if you get the front tranny stub shafts, c-clips, and left and right seals from the 04 6MT STi (available from the dealership, about $150 for all) you can use the SVX front axleshafts.

The gear ratios in the Spec B tranny are absolutely beautiful for the extra torque of the H6 motor. They have the best gear spacing and the tallest 5th and 6th gear.

All other factors will be the same from swapping auto to 6MT. Clutch and pedals, shifter, tranny mount will all still have to be fabbed up to work.

This swap is on par with the 06-07 STi 6MT for parts required. It is the most minimal swap there is as almost all drivetrain parts from the SVX can be retained. Again, the only thing you will not get is a front LSD or a DCCD center diff.

Any further questions ask away and I will check back.

fair enough. In the more experienced opinions of others, which is a better trans for a sporty daily driver that might a turbo at some point. STi 6, WRX 5, or Spec.b 6?

so, as i was writing that last post, i just noticed your post tireiron. That really answers alot of my questions.

I think your main problem will be finding one at a reasonable price, there are a lot fewer Spec B's out there than STi's. Brand new it will probably ring in somewhere around $3500 for the transmission alone. Also, I seem to recall something about the speed sensor being a different setup than the one in the SVX/STi, although I think there's a kit that will make it compatible. I love the transmission in my Spec B. 100 kph/62 MPH is around 22-2300 RPM. With a Kartboy short shifter and bushings it's a treat to drive.

One thing I'm not familiar with is the final drive setup. In the 2007 STi transmission I have in the SVX the FD is 3.90, but it uses a 3.54 rear diff. This is because in the AWD transfer there is a 1.1:1 reduction gear. I don't know if the Spec B transmission follows this principle or not. From what I've heard the internal construction is different from the STi, using narrower keyways on the gears for instance, so I don't know how far the mechanical differences go.

So all-in-all the Spec.B would be a great trans for the SVX, only downside being the loss of the front LSD, and the cost. Where ass the STi trans would be just as easy of a swap, but the gear are cut alot shorter that the spec.b... well this is all great info. I have to start doing some pricing and hunting for parts.

Couldn't you Frankenstein the Spec.B a little and add an LSD to the package?

Quote:

Originally Posted by Jade Dragon (Post 724266)

The JDM STi 6MT has much shorter gears, but the 2007 USDM isn't as bad. The only change between it and the Spec B are in 5th and 6th, the STi has 0.971/0.756 ratios and the Spec B has 0.819/0.707. Gears 1-4 are the same.

The unicorn of Subaru transmissions would be the JDM Forester STi. It's a full STi box with the Spec B ratios in 5th and 6th. DCCD, LSD, and long gears.

Another possibility is to get a STi 6MT (any flavor) and get the 5th and 6th gear parts from the dealer for a Spec B and have them put into the STi 6MT (be sure and confirm what parts are needed, it is more than just the gears based on what year tranny). Getting an 06-07 STi will still be the easiest and least parts requirement (uses SVX 3.54 rear diff) and swapping to the taller gears will get you all the STi goodies with the main drawing factor of the Spec B, the taller gears.

If you can afford the 6MT I would go that route and avoid the 5MT at all cost. I have quite a few friends that blow up the 5MTs pretty regularly with turbo H4s, nevermind the torque of the H6 and the extra weight of the car. The 6MT is a much more stout unit that is built correctly. The 5MT is built with 2 case halves and when the torque is applied to the gears they try and wedge apart and actually flex the case halves. This is what causes most failures of the 5MT. The 6MT is built like most other transmissions with one solid case that is loaded from the front and rear, so the wedging apart of the gears cannot cause the case to flex apart.

Going to a Spec B 6MT from the auto however you would not notice the missing front LSD or DCCD. Compared to the auto it will still be a much nicer ride with the viscous center diff and true AWD split (instead of the auto 90/10 split). So if you can find one it would not be a bad route to go for a nice weekend cruiser or daily driver.