This is not a new idea, in fact, there are people who buy brand new cars and within months they're contemplating switching to a manual transmission in favor of the automatic. Why, then, did they not opt for the manual to begin with?
This project deals with those who have a car that they're dedicated to, this is not a project for the faint or the meek. It's expensive, relatively complex, and can not be done with the tool kit you got for Christmas.
Why, you may ask, don't you just go buy a manual turbo? Easy answer: They didn't make wagons with the 5MT.
Why, you then ask, do you like wagons so much? Easy answer: They look better than the BC sedan, IMHO.
Why, you then wonder, would you spend this kind of dough on a turbo wagon? Easy answer: Because.
Why, you finally ask, don't you just rebuilt the automatic? Easy answer: It's just as expensive, rarely done right, and not as fun.
Oh. So this is about fun? Some of it, but for someone like myself who enjoys a spirited drive, passing buzzbox hondas and autocrossing, performance and control are arguably better with a pilot-selectable gear ratio. How's that easy answer?
Before i get into the gory details of what is necessary, there are a few things one must first consider before realistically proceeding with this project:
One: Replacing just the transmission is an option. I am going the extra mile and not only changing the transmission, but the clutch, flywheel and rear differential. Read on about these.
Two: Gear ratios. There are two gear ratios in the 5MT available from Subaru, 3.9 and 4.11. The 4.11 was reserved for the N/A version of the transmission and wasn't available in the Turbo models in the US. The 3.9 is the only ratio to be found in the Legacy Turbo, so any upgraded gearing would have to be done internally to the transmission, or by using a non-US transmission. It seems that most Australian/New Zealand models are 4.11.
Three: Clutch. Used clutches are a bad idea. I don't care if the transmission came with 10k miles or 100k, unless the clutch is obviously brand new or close to it, replace it. It is more expensive in labor than parts to replace the clutch, so drop a new one in while you've got it apart. It may add to your budget, but you won't regret it. This leads to...
Four: Flywheel. The stock one is fine, it's worked well so far, so what's wrong with it? It's unbelievably heavy: 26lbs, give or take. Most replacement Chrome-moly or aluminum versions are 10-16lbs. That's averaging 1/2 the weight of the original. Think about how large the flywheel is, what you may have heard about underdrive/lightweight pulleys and light wheels. More mass is bad, but more mass farther from the center of rotation gets progressively worse. By all accounts, a light flywheel is one of the most worthwhile upgrades available for any engine, period.
Now for the argument: Auto vs Manual.
Power: Basic knowledge of transmissions makes it clear that an automatic is not the most efficient way to deliver power to the driveline. In fact, modern transmissions are much better at this, but using hydraulics to transfer power is just...inefficient. Advantage: 5MT
Driveability: There's stop 'n go urban traffic, rural plodding and freeway cruising to consider here, but one must admit that one-footed driving, while boring, does have its advantages. Even left-foot brakers hardly have difficutly in traffic jams. Advantage: 4EAT
AWD: The main principle behind every Subaru built for the past 5 years, and heavily emphasized for the past 30, this is what people usually buy Subarus for. 4EAT is 90/10 most of the time, 50/50 in 1st and 2nd. The 4EAT uses electronics and sensors to keep an eye on the AWD system and make it work.. 5MT is 50/50 in all gears, and leaves the hard work up to viscous power transfer. I prefer simplicity, and consistency, and the possibility of 3 LSDs. Advantage: 5MT
Weight: The 4EAT uses ATF, and a LOT of it. It has not only an external filter, but a front-mounted cooler as well. It's also larger than the 5MT and so it must weight more. I know, it's a 3300lb car, but anything is helpful. Advantage: 5MT.
Longevity: This one is hard. I'm putting in a used transmission, sure, but these units go a LOT of miles when treated right, even with a lot of horsepower. There are Legacy Turbos with well over 250hp running stock gears still, after 10 years. Well prepped automatics will go for a long time, especially when cooled properly and made to shift harder and not slop as much. this is a toss up. Advantage: Tie
Big HP: This one isn't easy. Automatics can generally hold up much better to high horsepower when prepped right. Level 10 can make autos that'll withstand 900HP Supra drag cars. Sure there are "dog-gear" gearsets available, but it's expensive, hard to shift, and it's usually the transmission case flex that leads to the demise of Subaru gears. Advantage: 4EAT
Ok, 3/2 with one tie. I never said it was the choice, but it's not a bad one.
Now for the reality check. Just removing the transmission alone is a project, but now you're thinking about replacing an automatic with a manual. Here's a simple list of what would be needed for a basic swap, not including differential:
This is the simple list, but it encompasses the majority of parts needed.
Consider these when doing the swap:
New, improved clutch: You've gone this far, you probably
have a few more horsepower or are going to be getting more soon.
Parts i'm using:
91 Legacy Turbo 5MT transmission, 3.9 gear ratio.
The Exedy flywheel i got for a great deal. It's a chrome-moly unit that weighs somewhere around 14lbs, which is nearly half of the stock one. This will let the engine rev faster, and make the car quicker in first and second gears. The chrome-moly unit is also very resistant to wear, unlike the aluminum ones, so it should last for a very long time.
The GroupN disc was recommended by Richard because it was a compromise between power handling and street driveability. I'm also pleased that it's a genuine Subaru part (probably made by Exedy anyway). The pressure plate is actually from the non-US WRX, and was recommended for the same reasons as the disc. Paul Eklund of Primitive Racing switched to this at Richard's suggestion after breaking two ACT versions. It held up very well to a powerful car that's never driven softly. Replacement bearings are a no-brainer, always replace them.
I will likely get a Kartboy short shifter very soon. I'm interested in feeling what the stock shifter is like, compared to the short shifter, so i can make and objective comparison. I've heard that even the new stock ones weren't that great, so i'm sure this one will be a bit of a mess. It might actually be easier to replace the shifter once it's in the car. SPT/STi also has a full replacement assembly available, Richard can also get this, that isn't just a new shifter, but the linkage and all. It's surely a bit more work to install once the transmission is in the car, but i've heard very good things about it.
I do have plans to add an LSD at a later date. The LSD was an uncommon option in the Turbo, but they can be found. Other models also had the LSD available, so it makes the task of actually finding the parts a bit easier. The differential is actually a Hitachi unit, and was used in its various forms for as many years by Nissan. Datsun 510 owners frequently add LSDs from Subarus to their cars. The 300zx even had a version of this differential. In the interest of getting the car back rolling, i'm going to forego the differential tinkering.
Any pedal set from a Legacy or Impreza should do the job fine. The one i got was rusted, but it seems that's not uncommon from a salvaged car. The metal was probably unfinished, since it's inside the car and not usually exposed to the elements. It seems that most salvaged cars are missing at least some windows, so the metal gets oxidized badly. Fortunately, the part of the assembly that rusts is out of view. I do plan on investigating some rust remover and painting the part with a black spray paint to prevent further degradation.
The transmission crossmember is different between the automatic and manual, but i believe the Turbo and NA versions are identical, so getting the crossmember specifically for the turbo should be unnecessary.
I got a 91 transmission simply because it was one of two available with lower miles. There is a tag on the side of the transmission, which can be seen on the driver (left) side of the car from the engine bay, that can help determine what year and specification the transmission actually is. Following is a list of transmission gearings, and differential ratios. The breakdown of the codes is further down, thanks to Alex for these:
"OK! here is what i found. I have the 1992 Subaru Legacy service manual sitting in front of me."
"I also have the subaru parts manual (this was nice
score i might add) and what i read in the notes section about the rear
"I did a conversion from auto(1993) to manual(1991).
Since i'm not hearing
My transmission has the exact same TIN as Alex's, so we both have MY91 Turbo transmissions.
This wraps up the intro, head back and have a look at the actual swap information.