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  • converting an Impreza 2.5i to RWD

    I've found a few cheap hawkeye Imprezas (2.5i models, I mean) and I am curious about how to make it RWD only.

    I've done 2days worth of intensive online research and seems like there are lots of guys that weld up the center diff and ditch the front axles. However, this only saves a/b 20#s (best I have found) and leaves the 4wd trans/diff in place.
    Seems like you should be able to change to some 2wd tranny to shave more weight.
    I haven't been able to find the weight of the Subie 5MT -one guy said 135#s (with some other guys agreeing) but then someone else said it was +220#s. Anyone know the real weight?


    Don't bother posting "why would you do this?" or "Don't ruin a subaru!" yada yada yada...

    1. 2.5i Imprezas are CHEAP and they're not a performance car or very special
    2. N/A 2.5 seems to be a good mill, but it's overwhelmed by AWD and I don't wanna mess w/ Turbo(s)
    3a. I don't want FWD (for those who would suggest I get a honda or some other vehicle), I like RWD
    3b. I want 4doors and -other than old/high mileage Lexus IS or BMW 3- there aren't any affordable small sedans w/ RWD
    3c. I love the look of the hawkeye 2.5i (flat hood and no wing but they still have the boxy fenders)
    4. there's 18-25% driveline loss on awd vs. 10-15% DLL for RWD. On a 170HP motor an 8-10% WHP gain should feel pretty good

    can anyone think of a good (reliable and light weight) tranny to bolt to the 2.5 non-turbo Subaru block? Being inexpensive would be a great bonus.
    I've seen a few mentions of the tranny from an RX7, but whenever that's brought up someone will post that it's a pretty weak unit. (?)
    on a Nissan board someone said a Nissan RWD unit could work -anyone know anything about this?

  • #2
    Its almost cheaper and easier to do a STi swap. Basically the STi engine, tranny, axles, hubs, rear diff and ecu with harness.

    All the RWD conversions i've seen done are just like you said remove the front axles cover the front diff and call it good. You'd still have the weight of the 5 speed tranny

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    • #3
      Originally posted by da3bous View Post
      Its almost cheaper and easier to do a STi swap. Basically the STi engine, tranny, axles, hubs, rear diff and ecu with harness.

      All the RWD conversions i've seen done are just like you said remove the front axles cover the front diff and call it good. You'd still have the weight of the 5 speed tranny

      Ummm... STI swap is like $9k. I'm just looking for a possible tranny swap (hopefully less than $2k!). Plus, STI swap would include Turbo and OP shows I'm not really interested in effing w/ FI.

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      • #4
        Originally posted by Hillbilly View Post
        Ummm... STI swap is like $9k. I'm just looking for a possible tranny swap (hopefully less than $2k!). Plus, STI swap would include Turbo and OP shows I'm not really interested in effing w/ FI.
        Not really messing with FI if it stays stock, they are fairly reliable.


        Last time i checked the swap was in the 4-5K range without labor.

        To find a suitable tranny to work would be 2-3K, then you would need to make a new driveshaft, then you would need a new diff with the right gear ratio and the ability to withstand the abuse of it being the only diff. The whatever wiring you would need to figure out to tell the ECU that the center diff is fine.

        Also you might need to make an adapter plate for the tranny to mount to the engine and clear the current flywheel and clutch. Also modifying or getting a new clutch slave cylinder (push/pull). Also if you get a new tranny welding on the top bracket for a dog bone, most cars don't have this mount.

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        • #5
          Originally posted by da3bous View Post
          Last time i checked the swap was in the 4-5K range without labor.
          Labor is $3550 for the full swap (from the intake and harness all the way out to the hubs), I'm no superman w/ wrenches, and i've seen several posts showing that this isn't shadetree stuff to be done in a few w'kends.

          Originally posted by da3bous View Post
          To find a suitable tranny to work would be 2-3K, then you would need to make a new driveshaft, then you would need a new diff with the right gear ratio and the ability to withstand the abuse of it being the only diff. The whatever wiring you would need to figure out to tell the ECU that the center diff is fine.

          Also you might need to make an adapter plate for the tranny to mount to the engine and clear the current flywheel and clutch. Also modifying or getting a new clutch slave cylinder (push/pull). Also if you get a new tranny welding on the top bracket for a dog bone, most cars don't have this mount.
          This is the kind of info I'm interested in! I've never done anything more than test-drive a subaru, so I don't know anything a/b 'em other than what I read on Al Gore's interwebz...

          I can't imagine that I'd need some Tranzilla unit to transfer 160-200hp to rear wheels. Is there nothing out there in wreckingyardland w/ a similar size that can be hooked up cheaply?

          +are the rearends on these cars so weak that they can't take DD duty behind a mostly stock flat4?

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          • #6
            I think without going custom the only way is to weld the diff.
            Last edited by Tuck&Poke; 12-10-2010, 02:53 PM.

            ig: @jonnie86

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            • #7
              Sounds like a ridiculous way to "create" your car, just find something out there that you like. The AWD isn't that bad, it's the best part about Subarus and EVOs.
              1988 Toyota MR2 Supercharged
              Stance:Nation Feature | Build Thread

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              • #8
                Originally posted by Tuck&Poke View Post
                I think without going custom the only way is to weld the diff.
                Hope that's not the final answer, b/c it doesn't accomplish any of my goals...

                1. reduce weight
                2. reduce complexity
                3. reduce drivetrain loss to gain WHP

                Well, I may reduce some of the strain of the drivetrain (not having to turn extra wheels) but I'm really looking to have most efficient path b/t flywheel and ground.

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                • #9
                  Yeah a project like this should be more for someone that can tinker with it as things go wrong, because the first rule to remember in modifying a car is that it will no longer have stock problems.

                  If you aren't married to a car already then how about any of the other 4door RWD cars out there. What is your price point right now? What do you plan on doing with the car?

                  If it was me i'd be getting a subaru because i wanted an AWD car, thats the point of one really. Or if i wanted a RWD car i'd look at an E36 or E46....maybe even a manual C class. (all these are 4 door cars)

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                  • #10
                    Here is a quick explaination from Kumajubo from Team Orange. They run a rwd drift Impreza in D1


                    RWD Conversion
                    Although we have reinforced our D1 Imprezas with many beefier parts to withstand the massive 500-plus hp our cars make, I am simply going to talk about an easy RWD conversion that can be done by everyday Subie drivers. Most Subarus I see at my Ebisu Circuit are RWD-converted GC8s; however, the conversion method is the same for the GC, GDB, and Legacy.

                    The easiest way to convert your car to RWD is to remove the front drive shafts. This will lock the center differential and the car will then be RWD. You could remove the front differential, but then you would need to seal the transmission where the front drive shafts would be. Also, the speed sensor is driven off the front drive shafts, so for a simple conversion, the center diff and drive-splines for the front axles should be left in place. Also, the front drive splines on the wheel-side of the half-shaft need to be retained to maintain hub intergrity. These are the basics of a RWD conversion. You should now have a RWD Impreza!

                    That's not all!
                    You can drift by doing what I described above, however, because the Impreza's suspension was designed for an AWD car, the RWD-converted car will not react and handle like the RWD-based car you would buy from the dealership.
                    Below are our secret recipes we found for tuning the suspension. These made Team Orange champions! It took a while for us to discover these secrets, and I will only tell them to my Subiesport readers.

                    First of all, let's talk about handling characteristics.

                    Because the Impreza is an AWD-based car, it doesn't have much caster angle like a RWD-based car. In particular, Subaru's caster angle is near vertical. When you drivt with near vertical caster, the steering wheel won't re-center itself. It seems that Subaru's steering re0centers itself in large part due to the front part of the all-wheel drivetrain, which is lost in the RWD conversion.

                    You will need more caster angle to correct this behavior. First, you need to replace the attachment of the lower arms to ones of pillow ball type. You also need to stack some washers to move the lower arms forward along the body. By doing this, you will increase the caster angle, and the steering will re-center a little more.

                    Next, I will talk about the upper mount. This is an important aspect in improving the handling, and it will affect the caster angle as well as the camber angle. Usually, when you have a pillow upper mount, you can only adjust the camber angle, right?

                    But based on what I said earlier, you can increase the caster angle by moving the lower arms forward. With the pillow upper mount, you can increase the caster further.

                    For those using the GC coilover kit, you will need to change [the mount] to the ones for the GD. For those who are using the GD coilover kit, replace the pillow upper mount with that of the GC. In doing so, you can adjust the caster angle even more, and you will improve the handling a great deal.

                    Let's talk about improving and increasing the steering angle for drifters. This is most important. There is a method for fabricating a new knuckle, but unless you know what you are doing, I don't recommend you do it! It's too dangerous. There is also the common method of putting washers in, but you can't do that with our Impreza's since it will certainly destroy the rack.

                    What you really need is a rack from a FWD Impreza (it varies with model and year, so be sure to check first). Amazingly, these racks have more steering angle! I guess that Subaru made them like that so that the OBA-CYAN (grannies) can easily make U-turns on Japan's narrow streets!

                    By replacing the rack with one from a FWD Impreza, you will now have a more aggressive steering angle. If you open up the holes a little more insude where the tie rods attach to the knuckle, you will have the Team Orange setup. Am I telling you guys too much?

                    With these basics of front handling setups, you are now ready to dorifuto like us. However, there are smaller detail setup changes you can make. I thought that if I told you too much, maybe it wouldn't be as fun for your project, so I won't tell you anymore for now! But if you happen to get stuck with your RWD conversion project, I can probably help you more in a future column. In the up coming issue, I will talk about how to increase rear traction, so stay tuned!
                    Website | Facebook | Instagram @Broadway_Static

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                    • #11
                      Originally posted by kramerbuccs24 View Post
                      Sounds like a ridiculous way to "create" your car, just find something out there that you like. The AWD isn't that bad, it's the best part about Subarus and EVOs.
                      If you live in winterwonderland or have mucho hp to put to the ground AWD is fab.

                      I live in the south and am looking at an optimistic max of 200hp, so AWD is overkill for me.

                      AS for trying to create my car -I'm really not trying to re-invent the wheel, here. I like these cars, they're safe (have 2kids now, that's why I'm looking at moving the mustang to the backburner) and can be had for $9k-$12k. They look great stanced, too! What other reliable RWD sedan made since 2006 can be had w/ -50k miles in this price range?

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                      • #12
                        Originally posted by Average_Jerk View Post
                        Here is a quick explaination from Kumajubo from Team Orange. They run a rwd drift Impreza in D1


                        RWD Conversion
                        Although we have reinforced our D1 Imprezas with many beefier parts to withstand the massive 500-plus hp our cars make, I am simply going to talk about an easy RWD conversion that can be done by everyday Subie drivers. Most Subarus I see at my Ebisu Circuit are RWD-converted GC8s; however, the conversion method is the same for the GC, GDB, and Legacy.

                        The easiest way to convert your car to RWD is to remove the front drive shafts. This will lock the center differential and the car will then be RWD. You could remove the front differential, but then you would need to seal the transmission where the front drive shafts would be. Also, the speed sensor is driven off the front drive shafts, so for a simple conversion, the center diff and drive-splines for the front axles should be left in place. Also, the front drive splines on the wheel-side of the half-shaft need to be retained to maintain hub intergrity. These are the basics of a RWD conversion. You should now have a RWD Impreza!
                        ...
                        Wow, that was a lot of info. But not really what I'm after. I have read a/b converting the factory tranny to work RWD. BUT I'm interested to know if anyone is aware of a light(er) RWD tranny that would fit w/ a little work.

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                        • #13
                          You can get into an E46 330 or 325 for that price range, those were built up to 2006

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                          • #14
                            Originally posted by Hillbilly View Post
                            If you live in winterwonderland or have mucho hp to put to the ground AWD is fab.

                            I live in the south and am looking at an optimistic max of 200hp, so AWD is overkill for me.

                            AS for trying to create my car -I'm really not trying to re-invent the wheel, here. I like these cars, they're safe (have 2kids now, that's why I'm looking at moving the mustang to the backburner) and can be had for $9k-$12k. They look great stanced, too! What other reliable RWD sedan made since 2006 can be had w/ -50k miles in this price range?
                            You could get a Cadillac CTS, a Charger, a C class, 3 series, and prolly some others I'm forgetting. It just seems silly to talk about slight drivetrain loss or ~8hp when you're just looking for a DD and you're not modifying it for hp. Do what you'd like, obviously, that's just my opinion. Has nothing to do with "ruining the Subaru."
                            1988 Toyota MR2 Supercharged
                            Stance:Nation Feature | Build Thread

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                            • #15
                              Originally posted by da3bous View Post
                              You can get into an E46 330 or 325 for that price range, those were built up to 2006
                              [QUOTE=kramerbuccs24;298795]You could get a Cadillac CTS, a Charger, a C class, 3 series, and prolly some others I'm forgetting. [QUOTE]

                              I like all of those cars (except for the Charger) but -this is going to sound goofy- none of them fit me. I need something a little funky and the Impreza (in my head) fits nicely.
                              The Caddy is the closest to fitting me but they're auto-only (except for the bad-daddy V, which I can't afford).

                              Those are the main reasons. Then there's the fiscal reason -I can't really afford to mantain the BMW or the MBz (the two that can be had w/ MT).
                              the N/A flat4 @least gives the impression of being a motor you can work on w/o a degree in engineering. This is what I love a/b my 5.0mustang -even someone as simple as me can keep those running!

                              Originally posted by kramerbuccs24 View Post
                              It just seems silly to talk about slight drivetrain loss or ~8hp when you're just looking for a DD and you're not modifying it for hp. Do what you'd like, obviously, that's just my opinion. Has nothing to do with "ruining the Subaru."
                              Well there's something to that, but it seems like there's an 8-10% WHP increase. So, assuming it's possible to get the 2.5 to 200 flywheel HP, I'm looking at 170whp vs. 150WHP. Plus -what I imagine would be- greater fuel efficiency that comes from not having to operate all the extra drivetrain.
                              Last edited by Hillbilly; 12-10-2010, 03:58 PM.

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