K-swap Chronicles: EP3 Transmission

For those of you who have been following this blog, you know that I chose to go with an EP3 Si 5-speed transmission. Since this is an autocross car, 2nd gear top speed is crucial. While the typical transmission of choice is the 06+ Si 6-speed with LSD, the gearing was just too short for what I needed. Top speed on that trans in 2nd gear was around 53-55mph, which just wouldn’t have worked out for autocross. With the EP3 transmission, and rev limit bumped up to 8000rpm, I am able to hit almost 66mph in 2nd gear.

Here is the gearing chart for the 06+ Si trans

K24-Z3 Gearing

Here is the gearing on the EP3 trans

K24-EP3 Gearing

That grey line is very important for autocross, since that is where you spend 95% of your time.

Yesterday, I picked up a 5-speed transmission out of a 2005 Civic Si. I was a little bit skeptical, since this was the lowest priced one that I could actually find ($350), but the trans was only about an hour drive away so I was able to inspect it before purchase. According to the vehicle report, the car was totaled in December of 2012 and the mileage reading on the odometer was 78k miles. This all checks out with a third party report that I ran myself.

The input shaft spins without any grinding, and it shifts cleanly into each gear + reverse. It includes the clutch fork, slave cylinder, VSS Sensor, Reverse Sensor, and all attached mounting brackets. The seals are all in tact and there doesn’t appear to be any broken teeth on the VSS or inside the axle inputs. The shifter bushings will be replaced with aftermarket Hybrid Racing bushings, and the clutch lines will also be from Hybrid Racing.

Here are some pictures.

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Checking the shifting into each gear

1st

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2nd

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3rd

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4th

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5th

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Reverse

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The transmission will also receive brand new shifter cables from H-R, and gears will all be selected using the newest version of Hybrid Racing’s bolt-in fully adjustable shifter kit and delrin shift knob.

Here is the reverse sensor

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VSS

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And the clutch slave cylinder

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The transmission will also be cracked open to inspect everything and replace anything that needs it. It will also be fitted with a brand new MFactory helical LSD.

More updates to come!

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