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We bought a 91' Turbo Legacy that someone converted to a 5mt, with a 3.90 LSD. The trans was making some awful noises so we took it apart to find first gear on the input shaft toasted (it still worked 100%, just noisy as crap)... We then acquired two free donor transmissions hoping to make one good transmission out of three. We got a 06' WRX 5mt, and a Legacy 2.5GT 5mt (Not sure on year)...

The WRX trans had a blown 3rd 4th and 5th gear.

The Legacy GT had a blown up Pinion Drive Bearing which took out the case, and the drive pinion shaft.

I took the input shaft from the WRX since it was good, and pressed all of the gears off of it. Then I pressed the gears off the input shaft from the Legacy and installed them onto the WRX input shaft.

So WRX input shaft =
WRX 1st gear, WRX Reverse, WRX 2nd, Legacy GT 3rd and 4th gear. 5th gear came from our 91' Legacy.

I then took the Drive Pinion Shaft from the Legacy GT and pressed all of the gears off it that, along with the WRX. We left 1st, reverse, and 2nd installed on the WRX shaft, then pressed on the Legacy GT 3rd, and 4th. Then our 91' Legacy 5th gear was installed.

Used the WRX front diff and checked/set it.

Now, I have 2 rear cases sitting here and not sure which one to use. I am unsure if the trans that came with the car has a viscous coupling. The Legacy GT case if broken, but I bet the internals are good... Do I just throw on the WRX rear case?

Do I have to use a paper gasket to mate the rear case to the trans case? Or can I just use RTV?

You used the diff and drive pinion shaft off the WRX? Is the number on the side of your drive pinion gear matched to the number on the side of the ring gear on the diff?

One other thing... if you have a caliper, think you could give me some measurements on the drive-pinion adjustment plate you used to adjust the fore-aft shaft position?

The drive pinion shaft and diff are a matching set from the same 06' WRX transmission. I am unaware of any numbers on the shaft or the diff because I did not look for them. The ring gears on the diff of the Legacy 2.5gt and the WRX were the same tooth count wise.

The adjustments are shims, and I used three shims. Not sure what size they equal. If you want I can measure them when I get to work next week.. I got lucky, I grabbed 3 shims, threw them on and checked it... It was close enough for me! If it whines a little oh well, its a race car!

I was wondering how you decided how many shims to use. Did you check it using this guy?: http://bbs.legacycentral.org/viewtopic.php?t=40986

If you have that sucker, mind giving me a few measurements? The fore-aft measurements are the only ones that are really important.

fishbone79 wrote:I was wondering how you decided how many shims to use. Did you check it using this guy?: http://bbs.legacycentral.org/viewtopic.php?t=40986

If you have that sucker, mind giving me a few measurements? The fore-aft measurements are the only ones that are really important.

I do not have that nor did I knew it existed! I just laid the shaft in and looked at how everything meshed. Painted the ring with some anti-seize, preloaded the diff and spun the pinion shaft. Then checked the wear patterns like you would a rear end. I am sure I did not do it the "proper" way, but I am confident it will work. I took a shim out to see how it effected it, then added a shim to see what it looked like. Just did that till I was happy with the pattern.

The WRX rear case has a reduction gear, changing the final drive. I think.

Yeah, we figured this out. I put back in the 3.90 front diff and drive pinion that came out of it and will also put on the original rear case so everything matches.