Boxing-tough: a six-speed gearbox will let you drive your Subaru like you're Colin McRae

Boxing-tough: a six-speed gearbox will let you drive your Subaru like you're Colin McRae

Recently we swapped a 6 speed STI gearbox into the 1999 2 Door WRX STI. Check out the video here: 

The original joke Nissan drivers told about go-fast Subarus is they came with glass gearboxes. Early WRXs ('93-'97) and Libertys definitely spent plenty of time on the back of tow trucks with 1st or 2nd gear sitting in the transmission pan thanks to bulk grip, plenty of power, and a weak design.

This led to the afternarket taking a leaf out of the rally book, with straight-cut gearsets replacing the factory helical 1st-4th gears. There was also dog-engagement boxes, which could allow near-clutchless gear-changes but were also difficult to drive compared to normal synchromesh transmissions.  

While later 5-speed manuals got tougher they don't hold a candle to the "unbreakable" six-speed manual which debuted in the GD-series STi Impreza. With design input from Porsche Engineering the 6-cog 'box is physically wider and much, much heavier than the 5-speed.

Among many upgrades the 6-speed boasts an oil pump (for improved lubrication), fatter gears and improved synchromesh for faster shifting performance, while the clutch and flywheel have a larger diametre, providing more surface area to clamp on. Some STi models also featured front limited-slip diffs (for a maaaad handling upgrade), and an adjustable centre differential called Driver Controlled Centre Differential (DCCD). 

Thanks to Subaru's inherent Lego nature the 6-speed provided a bolt-in upgrade for Libertys, Foresters, Imprezas, and Outbacks, connecting to both 4- and 6-cylinder engines, and connecting to factory tailshafts. This meant you didn't need a noisy aftermarket gearset fitted to your original gearbox, you had a factory solution with an extra gear for sweet freeway cruising. 

One of the downsides, apart from the weight of the 6-speed, was the cost. A decade ago a 6-speed swap would run nearly $10,000, though this has halfed today. If you then also fitted the full R180 rear-end from an STi that could add several thousand dollars more, though it truly provided a nuclear-tough drivetrain you could abuse even with 300kW at the wheels.  

If you're wondering why someone would spend so much changing their gearbox and diff for another factory unit, one 7000rpm launch should cure any doubts you have!


3 comments

  • George

    Would this swap work on a bh5 legacy/liberty?

  • André Klauset

    Ben, you can get hybrid axles but they cost more than they are worth, get a set of 04/05 sti rear hubs as they are 5×100. Then you just need “gravelspec” rear rotors to accomodate the sti’s 190mm handbrake (wrx has 170mm) and the wrx 4/2 pot.
    The hybrid axles are aprox 1000 usd last time i checked, cheaper and better to swap hubs.

    I’ve done this myself in my 350whp bugeye wagon with a full 04 sti dccd driveline swap while keeping the wrx brakes.

  • Ben Jones

    A 6 speed conversion on my bugeye wagon is a dream of mine but was wondering about the r180 diff. Is it possible to keep your WRX hubs as I hear the 180 has different splines? I was thinking about the possibility of hybrid rear driveshafts could u just get sti inner CV joints and fit them to WRX driveshafts? Any info at all on the subject would b awesome as I’m prepared to do a hub swap & very eager to learn more about modifying my project car but I’m on a tight budget as I have 5 kids.

    Also I understand that you boys are very busy so I won’t b offended if u don’t have time for this.

    Keep doing what you’re doing as its amazing
    Ben Jones

Leave a comment