The CUSCO 317-028-AR is a close-ratio gear set designed for the Honda Civic EG6 / EK4 / EK9 transmission family. CUSCO lists it specifically as TYPE-R.
🔧 The key idea
It isn’t simply a stronger gearbox. Its main purpose is to reshape the gear ratios so the engine loses less RPM between shifts, keeping a naturally aspirated B-series engine closer to its useful power band.
|
Gear |
CUSCO 317-028-AR |
EG6/EK4/9 STD |
|
1st |
2.533 |
3.230 |
|
2nd |
1.944 |
2.105 |
|
3rd |
1.590 |
1.458 |
|
4th |
1.280 |
1.107 |
|
5th |
STD |
0.848 |
|
Final |
STD |
4.400 |
CUSCO’s published specifications confirm those ratios.
🧠 Why TYPE-R is interesting
The really clever part is the 2nd–4th gear progression.
The standard gearbox has relatively large ratio changes. The CUSCO set makes the middle gears substantially closer:
STD:
3.230 → 2.105 → 1.458 → 1.107
CUSCO AR:
2.533 → 1.944 → 1.590 → 1.280
So during a hard acceleration shift:
Engine RPM ↓ less → engine stays nearer its torque/power zone → acceleration resumes sooner.
That’s particularly attractive for a high-revving B16A/B16B because these engines reward keeping RPM high.
⚡ What changes on an EG6?
Think of it this way:
Standard gearbox
1st → big RPM drop → 2nd → bigger drop → 3rd → 4th
317-028-AR
1st → tighter 2nd → tighter 3rd → tighter 4th
The trade-off is that the 2.533 first gear is much taller than the 3.230 standard first gear. So the car gives up some first-gear multiplication in exchange for a more motorsport-oriented progression.
This is why I’d characterize the AR as a circuit/spirited-driving-oriented ratio set rather than an automatic “more acceleration everywhere” modification.
🏁 AR vs AC vs AS
CUSCO offers three different concepts for this Civic application:
- 317-028-AS — TYPE-S: 3.417 / 2.412 / 1.714 / 1.231 / STD
- 317-028-AC — TYPE-C: 2.533 / 1.944 / 1.590 / 1.280 / 1.032
- 317-028-AR — TYPE-R: 2.533 / 1.944 / 1.590 / 1.280 / STD
The AR is especially interesting because it keeps the standard 5th gear, whereas the AC also changes 5th to 1.032.
Key takeaway:
317-028-AR = less about “making the gearbox stronger” and more about turning the B-series drivetrain into a closer, higher-RPM acceleration machine.
It makes the most sense when the engine, differential/final drive and driving environment are all chosen around the new ratios.
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