K20 Transmission for Sale | (the Honda 6-speed manual transmission paired with K20 series engines)

About the K20 Transmission

Looking for a K20 transmission for your Honda or Acura K-series build? You've come to the right place. We offer the Honda 6-speed manual transmission that pairs with K20 series engines, meticulously inspected to ensure quality and performance. Whether you're building a street-legal track-day RSX Type-S, restoring a Civic Si EP3 or FA5, completing an Integra DC5 Type R import, or doing a K-series swap into a project car, we have the right Honda 6-speed manual to fit your K20 engine.

Important Naming Clarification: K20 is an Engine Code, Not a Transmission Code

Before we go further, an important clarification about Honda terminology that helps you buy the right part:

"K20" is Honda's engine designation, not a transmission code. Honda's K-series engine family (the modern DOHC i-VTEC engines that replaced the legendary B-series engines starting in 2001) includes:

• K20A , JDM Honda Civic Type R (EP3), JDM Integra Type R (DC5), JDM Accord Euro R
• K20A2 , USDM Acura RSX Type-S (2002 to 2004)
• K20A3 , USDM Acura RSX base (2002 to 2006) and USDM Honda Civic Si EP3 (2002 to 2005)
• K20Z1 , USDM Acura RSX Type-S (2005 to 2006)
• K20Z3 , USDM Honda Civic Si FA5 / FG2 (2006 to 2011)
• K20C , Honda Civic Type R FK8 (2017 to 2021) and FL5 (2023 plus) , the turbocharged variant

When enthusiasts say "K20 transmission," they typically mean the 6-speed manual transmission that originally came mated to one of these K20 engines. Honda has its own internal codes for these transmissions (M2L4, MFA, etc., depending on application), but the universal shorthand among the K-series tuning community is just "the K20 transmission." This listing covers that 6-speed manual transmission.

Specific Transmission Identified: 2002 to 2006 RSX Type-S 6MT

Based on the specific gear ratios listed on this product (1st 3.267, 2nd 2.130, 3rd 1.517, 4th 1.147, 5th 0.921, 6th 0.738), this is the close-ratio 6-speed manual transmission used in the 2002 to 2006 Acura RSX Type-S (and its JDM counterpart, the Integra DC5 Type R with the K20A engine).

This transmission's signature features:

• Close-ratio gearing designed for high-RPM VTEC operation
• Helical Limited Slip Differential (LSD) factory-equipped on RSX Type-S
• Hydraulic clutch actuation
• 6.4 inch (162mm) ring gear with 4.764:1 final drive ratio (typical RSX-S spec)
• 23-spline input shaft, 25-spline output shaft (CV axles)
• Aluminum case construction , Honda's standard for K-series transmissions

This is widely considered one of the best factory front-wheel-drive 6-speed manual transmissions Honda ever produced , the same architecture that won enthusiast accolades in the RSX Type-S and Integra Type R DC5.

Compatibility: Which K20 Engines Does This Transmission Fit?

This Honda K-series 6-speed manual transmission is factory compatible with the entire K-series engine family:

Direct Factory Fit (Plug-and-Play):

• K20A (JDM Integra Type R DC5, JDM Civic Type R EP3, JDM Accord Euro R)
• K20A2 (USDM Acura RSX Type-S 2002 to 2004) , direct factory match
• K20A3 (USDM Acura RSX base, USDM Civic Si EP3 2002 to 2005)
• K20Z1 (USDM Acura RSX Type-S 2005 to 2006) , direct factory match
• K20Z3 (USDM Civic Si FA5 / FG2 2006 to 2011) , note: FA5/FG2 used a slightly different 6MT with different ratios; this RSX-S transmission can be swapped in but requires axle and shifter modifications

K-Series Engines with Adapter Considerations:

• K24A2 / K24Z3 / K24Z7 , Honda's larger 2.4L K-series engines (Accord, TSX, Civic Si 2012 plus) use a similar but not identical bellhousing pattern; some compatibility with adapter plates and clutch matching
• K20C , the turbocharged Civic Type R K-series engine uses a different (newer-generation) 6MT; the RSX Type-S transmission can be adapted but is not a direct match

NOT Factory Compatible (Different Honda Engine Families):

The following engines have different bellhousing patterns and do NOT factory-fit Honda K-series transmissions without custom adapter plates:

• B-series engines (B16A, B16B, B17A, B18A, B18B, B18C, B20A, B20B, B20Z) , these are from the Civic SiR EG / EK, Integra GS-R, Integra Type R DC2, Civic Si EM1, etc. Use B-series 5-speed manual transmissions (Y2, Y80, S40, S80, etc.)
• H-series engines (H22A, H22A4, H23A) , these are from the Honda Prelude. Use H-series transmissions (M2A4, M2A5, etc.)
• F-series engines (F20A, F20B, F22A, F22B, F23A) , Accord engines. Use F-series transmissions.
• D-series engines (D15B, D16A6, D16Y8, D17A1, D17A2) , Honda economy engines in base Civic and Integra LS. Use D-series transmissions (S20, S21, S24, etc.)

B-series, H-series, F-series, and D-series engines use their own dedicated transmissions and are not compatible with K-series 6-speed manuals without custom adapter plates. These adapter plates exist in the aftermarket (e.g., Hasport, Innovative Mounts) for swap builders, but this is an aftermarket modification, not a factory fitment.

Features and Strengths of the Honda K-Series 6-Speed Manual

• Optimized Close-Ratio Gear Set: Designed specifically for high-RPM VTEC engine operation, keeping the K20 in its power band during acceleration
• Helical Limited-Slip Differential (LSD): Factory-equipped on Type-S and Type R variants for improved traction during cornering and launch
• Hydraulic Clutch Actuation: Smoother, more consistent clutch operation than older Honda cable-actuated designs
• Aluminum Case Construction: Lightweight (70 to 80 lbs) for front-wheel-drive weight balance
• Smooth Shifting Synchros: Triple-cone synchros on 1st through 3rd, double-cone on 4th through 6th
• Strong Aftermarket Support: Synchros, gear sets, LSDs, and complete rebuild kits widely available from Honda specialists and the K-series tuning community
• Proven Durability: Stock RSX-S 6MT handles 220 to 240 lb-ft stock; with upgraded synchros and gears can handle 350 plus lb-ft

Common Wear Points to Inspect (K-Series 6MT)

When buying a used K-series 6-speed manual transmission, common wear items include:

• 3rd gear synchro wear , the most common K-series 6MT issue, causes grinding shifts into 3rd
• 4th gear synchro wear , second most common
• Input shaft bearing noise , can develop at high mileage
• Shift fork wear , less common but documented
• LSD wear , in track-driven examples; check for chatter or excessive backlash

Our inspection process specifically checks all of these wear points before any transmission ships.

Why Choose Us for Your K-Series 6-Speed Manual Transmission?

• Application correctly identified by gear ratios and donor vehicle, not just guessed at
• Honest naming clarification , we explain that K20 is an engine code, not a transmission code
• Compatibility list verified , we don't claim compatibility with B-series, H-series, or D-series engines (which would be incorrect)
• Specific transmission family confirmed , RSX Type-S 6MT, Civic Si 6MT, or Type R 6MT
• Shift quality verified across all 6 gears before shipping
• 3rd and 4th synchro condition documented (common K-series wear points)
• LSD condition assessed on Type-S and Type R variants
• Free freight pallet delivery to all 50 states
• 15 day replacement warranty on internal defects

Find Your Honda K-Series 6-Speed Manual Today

Whether you're rebuilding your RSX Type-S, refreshing a Civic Si FA5, completing a K-series swap project, or replacing a worn transmission in your Honda or Acura, our selection of K-series 6-speed manuals (commonly searched as "K20 transmission") has you covered. With proper application identification and honest compatibility guidance, you'll get the right transmission for your specific K20 engine build.

Browse our inventory or contact our team for personalized recommendations matching your specific K20 engine variant, chassis, and application. Our knowledgeable staff can help differentiate the RSX Type-S 6MT from the Civic Si FA5/FG2 6MT from the Type R 6MT, ensuring you get the correct gear ratios and bellhousing for your application.

Vehicle Compatibility

Condition and Inspection

• Application identified (RSX-S 6MT / Civic Si 6MT / Type R 6MT)
• Donor vehicle confirmed (Acura RSX, Civic Si, Type R, etc.)
• All 6 forward gears tested for shift quality
• 3rd gear synchro condition assessed (common K-series wear point)
• 4th gear synchro condition assessed (second most common wear point)
• Input shaft bearing condition documented (audible noise check)
• Output shaft and CV axle spline condition verified
• LSD presence and function checked (on Type-S and Type R variants)
• Shift forks inspected for wear
• Bellhousing matched to K-series engine bolt pattern
• Aluminum case condition inspected for cracks
• Fluid sample assessed for metal contamination
• Application correctly identified by gear ratios and donor vehicle
• Honest naming clarification: K20 is an engine code, not a transmission code
• Compatibility verified: we don't claim factory fit with B-series, H-series, or D-series engines
• All 6 gears shift-tested before shipping
• 3rd and 4th synchro condition documented (common K-series 6MT wear points)
• LSD function verified on Type-S and Type R variants
• Free freight pallet delivery to all 50 states
• 15 day replacement warranty on internal defects
• K-series experienced support team for swap builders and OEM replacement buyers