V3 sti gearbox swap

Discussion in 'Projects, modifications & how to guides' started by AutoSource, Dec 4, 2018.

  1. AutoSource

    AutoSource V-Limited Member

    New Zealand
    Hey so I have an sti v3 that has had a 04 forester gearbox put in it. Factory the car should have a 752 box and I’m going to put a v5/6 754 in it. Wanting to know if everything like axles and gear linkages, drive shaft etc will just slot straight in if I buy the 754 box? Or will they be from a forester and I need to find everything for a wrx? Cheers
  2. 1509joe

    1509joe V-Limited Member

    Need a lot more info than that Boss.
  3. edsel

    edsel V-Limited Member

    Not being savvy with forresters I wouldn't know the rear diff ratio.
    I had a 754 box in my ra for a while, I used the 754's diff and linkage. I've bought three used gear boxes in the past and they all came with linkages. Matching the box, diff and shafts is the big concern
  4. Paul92

    Paul92 V-Limited Member

    Your STI should originally have a short throw shifter but that works on any 5MT. I guess the Forester has a 754 5MT transmission but you should indeed check the diff.
    If you upgrade to a R180 diff you need to replace the rear shafts, mounts, hubs, you name it. Prop shaft will fit though.

    I kind of lack knowledge of gearboxes and rear diffs if it comes to the ratio. Is it safe to say that it's because of the front/center and rear diff need to match?

    For example, I can imagine the gear ratio itself of a '95 WRX is different than that of a STI RA from the same year even though they both have a TY752 box and a R160 4.111 rear diff.
    So basically a V4 R160 3.54 LSD would not work on a '95 WRX transmission?
  5. AutoSource

    AutoSource V-Limited Member

    New Zealand
    Thanks for the help. The v5/6 gearbox and forester gearbox currently fitted have the same diff ration 4.44 so hopefully it’s just a matter of removing the old and in with the new. I have bought the replacement gearbox so will have a crack over the next few weeks.
    Anything that doesn’t match up I guess I’ll have to deal with as I go.
  6. AutoSource

    AutoSource V-Limited Member

    New Zealand
    Job done now. Everything went together fine the only part that didn’t cross over was the front drive shafts/axles. The later model forester gear box takes the cv spline inside it where the Impreza gearbox has the splines coming out of the gearbox. Also discovered that any Impreza axles of a similar era will work - I used a pair from a 99 Impreza 2wd drive 1500cc automatic.
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  7. It might be worth creating a thread with pics (if you have any) of the swap as it could be very useful for other members in the future(?)

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