MFactory 6 Speed K Series Final Drive Gear Set for K20/K24

MFactory Final Drive Gear Set - K20 & K24 6-Speed (4.00, 5.08, 5.41)

A final drive change multiplies the power you already have through every gear in the box. On a K-series that's already willing, that's the difference between a car that pulls well and one that feels genuinely urgent. Three ratios available, and unusually for a final drive, one of them goes the other direction. Worth understanding which is which before you order.

Check Your Starting Point First

This matters more than usual here, because these transmissions didn't all leave the factory the same.

That 02-04 RSX difference is significant. Coming from 4.389, a 5.08 is a moderate step. Coming from 4.764, the same 5.08 is a smaller change. Same part, different outcome depending on your car.

Which Ratio, And Why 4.00 Is Different

Two of these shorten your gearing and one lengthens it. Know which you're buying.

5.41 (MFT-TRS-02K54) is the aggressive short ratio. Serious torque multiplication in every gear, built for autocross, tight technical tracks, and drag applications where you're living in the low gears and top speed doesn't matter. On the highway you'll be spinning noticeably high rpm.

5.08 (MFT-TRS-02K50) is the middle ground. A real improvement in acceleration while staying more livable than the 5.41. This is the popular choice for a car that sees track days and still gets driven on the road.

4.00 (MFT-TRS-02K40) goes the other way entirely. It's taller than any of these cars came with, which means longer gearing, lower rpm at speed, and higher top speed per gear. That's not what most people want, but it's exactly right for high speed circuits, standing mile events, or a boosted build making enough torque that stock gearing has the car running out of gear too quickly.

Be clear on which problem you're solving. Most people shopping a final drive want shorter. If you specifically need longer, the 4.00 is the one, and it's an unusual and useful option to have.

02-04 RSX Owners Need An Extra Bearing

Read this before ordering, because it's an additional part.

Fitting this final drive to a 2002-2004 RSX requires the 35mm countershaft bearing from an 05 or later model. The earlier transmissions use a different bearing, and the gear set is built around the later spec.

We stock it, Honda part 91005-PPS-003, so add one to your order and you're covered. Everyone else, 05-06 RSX, TSX, and Civic Si, is fine with what's already in the transmission.

Pair It With A Limited Slip

Worth thinking about seriously, because it's where a lot of the gain gets realized.

More torque multiplication means more torque at the wheels, and on a front-drive car with an open differential that often just means more wheelspin from the unloaded side. A shorter final drive can genuinely make an open-diff car worse out of a corner, since you're feeding more torque into a system with no way to manage it.

The MFactory K-series limited slip differential (MFT-TRS-05K20) sends that torque to the wheel with grip instead. And practically, both parts require splitting the transmission case, so doing them together means one job rather than two on a gearbox that has to come out of the car either way.

What Else To Sort While You're In There

Your speedometer will read wrong. Changing the final drive changes output speed relative to your wheels, so the speedo and odometer will be off. Plan on a correction.

Inspect bearings and seals. Anything you remove to reach the ring gear should go back in fresh if it has real miles on it. They cost almost nothing next to the labor of getting to them.

Look at your synchros. If the transmission has started grinding, this is the moment to deal with it rather than pulling the box again in a year.

Mention it to your tuner. Gearing changes how load builds in each gear, so if the car is tuned it's worth a conversation.

Fitment

2002-2006 Acura RSX Type-S
2004-2008 Acura TSX
2006-2011 Honda Civic Si

Fits K20 and K24 6-speed manual transmissions, including K20A2, K20Z1, K20Z3, and K24A2, plus EP3, FN2, and FD2 applications. 02-04 RSX requires the 35mm countershaft bearing (91005-PPS-003).

Who Should Run One

This is for the K-series owner who wants the car to accelerate harder without touching the engine, or who's gone the other direction and needs taller gearing for high speed use. Either way you're changing what the transmission does with the power you already have, which on a good engine is often better value than chasing more of it. Check your starting ratio, add the bearing if you're in an 02-04 RSX, and pick the direction you actually need.

Fits: K20 and K24 6-speed manual transmissions in the 2002-2006 RSX Type-S, 2004-2008 TSX, and 2006-2011 Civic Si, plus EP3, FN2, and FD2. Part numbers: MFT-TRS-02K40 (4.00), MFT-TRS-02K50 (5.08), MFT-TRS-02K54 (5.41). 02-04 RSX also requires: 35mm countershaft bearing, Honda 91005-PPS-003. Speedometer correction required. Pairs with: MFactory K-series LSD (MFT-TRS-05K20).