Best Transmission For Go Kart: 30-Series and 40-Series Gearboxes

#1 · Best Overall

1. maXpeedingrods 30 Series Gearbox

• Dimensions: 7.87 x 7.87 x 7.87 in
• Weight: 12.35 lb

Best for: 30 Series Chain Flexibility.

Why it ranks #1: Supports engines up to 14HP and specifies a 5/8-inch keyed shaft plus sprockets for #35 and #40/41/420 chain.

Included 12-tooth and 10-tooth sprockets let this 30 Series gearbox work with #35 chain or #40/41/420 chain, giving builders a choice when matching a go-kart drivetrain. It supports engines up to 14HP and supplies forward and reverse operation for go-karts and utility vehicles.

The 5/8-inch shaft with a 3/16-inch keyway identifies the clutch-side interface, while the two included sprockets cover the listed chain options. Its gearbox speed is 5/13 of clutch speed, and the listed forward and reverse ratios are 1:1:3 and 1:2:6. A 1540mm shifter cable gives the installer a specified cable length to plan around. The central fit boundary is explicit: this gearbox is for 30 Series use, not other series.

Skip it if you need a 40 Series gearbox for an 11–18HP engine; Leyuncot's 40 Series kit lists that application.

Choose this kit when a 30 Series go-kart or utility-vehicle build needs forward and reverse, with a chain choice between the included sprocket options. Keep the 14HP ceiling and 30 Series restriction central to the fit decision.

Listed on Amazon as: maXpeedingrods Go Kart Forward Reverse Gearbox Kit 212cc 30 Series

#2 · Broad Engine Range

2. GXYWADY 30 Series Gearbox

• Dimensions: 7.87 x 7.87 x 7.87 in
• Weight: 12.45 lb

Best for: Compact 30 Series Neutral.

Why it ranks #2: Covers 2–13HP engines and lists three shift modes, a 5/8-inch shaft, and sprocket options for multiple chain sizes.

Forward, reverse, and neutral selection gives this GXYWADY 30 Series gearbox a useful operating range, enabling easier maneuvering on a compatible go-kart. The listing covers 2HP–13HP engines and includes sprockets for #35 and #40/41/420 chain, accommodating several specified drivetrain configurations.

The three shift modes add neutral as well as forward and reverse, while the 5/8-inch shaft and 3/16-inch keyway identify the listed connection dimensions. Its 12-tooth and 10-tooth sprocket options correspond to #35 and #40/41/420 chain, helping builders match the chain already used. The kit is specified for a 30 Series torque converter and 2HP–13HP four-stroke engines. Those limits make series, engine type, and chain the key fit checks.

Skip it if you need a 40 Series gearbox for an 11–18HP engine; GXYWADY's 40 Series replacement lists that engine range.

This is a fit for a 30 Series four-stroke kart build that needs three shift positions and uses one of the listed chain options. Its 13HP ceiling and torque-converter series requirement define the compatibility boundary.

Listed on Amazon as: GXYWADY Forward Reverse Gearbox Kit Replacement for 2HP-13HP Go Kart

#3 · Clear Shift Ratios

3. Silscvtt 30 Series Gearbox

• Dimensions: 9.06 x 7.68 x 7.68 in
• Weight: 12.35 lb

Best for: 30 Series Cable-Controlled Shifting.

Why it ranks #3: Lists forward and reverse ratios, a 5/8-inch shaft, 2300 RPM, and three shift positions for engines up to 13HP.

A 1540mm shifter cable and three-position selection give this Silscvtt 30 Series gearbox a defined control setup, enabling forward, reverse, and neutral operation. It supports engines up to 13HP and lists sprocket compatibility with #35 or #40/41/420 chain for matching common kart configurations.

The 5/8-inch shaft and 3/16-inch keyway specify the driven-clutch connection, while the 1540mm cable length helps plan the shifter route and control placement. Forward and reverse ratios are listed as 1:1.3 and 1:2.6, with an RPM figure of 2300. The gearbox supports up to 13HP and the listed chain choices. Silscvtt expressly limits use to 30 Series, so it is not a substitute for a 40 Series unit.

Skip it if you need a 40 Series gearbox for Predator 420cc and 530 chain; Leyuncot's 40 Series kit specifies that setup.

This suits a 30 Series kart up to 13HP when the shaft, chain, and cable length work for the existing layout. Do not select it for a 40 Series drivetrain; that restriction is explicit.

Listed on Amazon as: Silscvtt 30 Series Go Kart Forward Reverse Gearbox

#4 · Multiple Sprockets

4. labwork 30 Series Gearbox

• Weight: 5600 g

Best for: 30 Series Assembly Projects.

Why it ranks #4: Targets 2–13HP engines and states compatibility with 10T 40/41 and 12T 35 sprockets, plus a 1540mm shifter cable.

A 1540mm shifter cable and stated easy-installation workflow make the labwork 30 Series gearbox a practical candidate for hands-on kart assembly. The listing covers 2HP–13HP four-stroke engines and specifies replacement sprockets for 10-tooth 40/41 and 12-tooth 35 chain configurations.

The 30 Series torque-converter fitment and 2HP–13HP four-stroke engine range define the main application limits, while the 10-tooth 40/41 and 12-tooth 35 sprockets address two chain setups. Its gearbox speed is listed as 5/13 of clutch speed, and the 1540mm cable gives a specified length for shifter planning. The listing also describes installation as easy for people assembling karts. Match the engine, converter series, and chain before fitting.

Skip it if you have an 11–18HP 40 Series kart with 530 chain; Leyuncot's gearbox lists that engine and chain combination.

This fits a builder assembling a 30 Series kart within the stated engine range, especially when the listed sprocket and cable details suit the layout. The four-stroke and series limits should guide compatibility checks.

Listed on Amazon as: labwork Go Kart Forward Reverse Gearbox Kit Replacement for 2HP-13HP Engine

#5

5. ALL-CARB 30 Series Gearbox

• Dimensions: 7.09 x 7.09 x 7.09 in
• Weight: 12.28 lb

Best for: 30 Series Ratio-Specified Builds.

Why it ranks #5: Specifies 2–13HP engines, a 5/8-inch keyed shaft, and #40/41 and #35 chain sprocket fitment for a 30 Series setup.

Specified forward and reverse ratios of 1:1.3 and 1:2.6 give this ALL-CARB-listed gearbox a clearly defined operating setup for 30 Series kart builds. It supports engines from 2HP to 13HP and lists 10-tooth #40/41 and 12-tooth #35 configurations for drivetrain matching.

The 5/8-inch shaft with a 3/16-inch keyway identifies the clutch connection, while the two sprocket options correspond to #40/41 and #35 chain. Listed ratios of 1:1.3 forward and 1:2.6 reverse, plus an RPM figure of 2300, describe its operating specifications. The 51.18-inch (130cm) shifter cable provides a stated length for control placement. Its 30 Series fitment and 2HP–13HP engine range define the main compatibility boundaries.

Skip it if you need a 1540mm shifter cable; Silscvtt's 30 Series gearbox lists that longer cable length.

Choose this for a 30 Series go-kart within the 2HP–13HP range when its ratios, keyed shaft, chain options, and 130cm cable suit the build. Cable routing and drivetrain fit remain important boundaries.

Listed on Amazon as: ALL-CARB Go Kart Forward Reverse Gearbox Replacement for 2HP-13HP

#6

6. JNDO 30 Series Gearbox

• Weight: 12.1 lb

Best for: Three-Position DIY Builds.

Why it ranks #6: Offers forward, neutral, and reverse modes and states support for engines up to 13HP, including 420cc applications.

Forward, neutral, and reverse modes give the JNDO 30 Series gearbox three distinct operating selections, enabling maneuvering that a forward-only kart cannot provide. Its stated engine coverage reaches 13HP or 420cc, making it an option for builders seeking added reverse functionality on a compatible DIY assembly.

The three shift modes provide a neutral selection alongside forward and reverse, supporting more flexible low-speed maneuvering during operation. JNDO lists compatibility up to 13HP (420cc), which gives builders a stated upper engine boundary when selecting a gearbox. The description also identifies DIY assembly enthusiasts as its audience, so installation planning belongs in the build process. The supplied information does not specify shaft dimensions, chain size, or sprocket details; verify those against the kart setup before choosing.

Skip it if you need a stated shaft size and 530-chain setup; Leyuncot's 40 Series gearbox specifies both.

This suits a DIY builder adding reverse and neutral to a 30 Series kart with an engine within the listed 13HP or 420cc limit. Treat unspecified shaft and chain details as a key compatibility boundary before committing to the installation.

Listed on Amazon as: JNDO Go Kart Forward Reverse Gearbox Kit 30 Series for 212cc 420cc Engine

#7

7. SEBLAFF 30 Series Gearbox

• Dimensions: 7.87 x 7.87 x 7.87 in
• Weight: 12.35 lb

Best for: Compact 212cc 30 Series.

Why it ranks #7: Fits listed 2–13HP 30 Series applications and specifies #35 12T and #40/41 10T chain sprocket options.

A compact assembly and stated convenient installation make the SEBLAFF 30 Series gearbox an option for builders fitting a forward-and-reverse transmission to a 212cc kart. It is listed for 2HP–13HP engines and for #35 or #40/41/420 chain, with corresponding 12-tooth and 10-tooth options.

The 30 Series torque-converter fitment and 2HP–13HP engine range establish the main compatibility limits for a replacement or new kart build. Its chain listing covers #35 with a 12-tooth sprocket and #40/41/420 with a 10-tooth sprocket, helping a builder select the matching drivetrain configuration. SEBLAFF describes the assembly as compact and installation as convenient, which may simplify packaging and fitting work. The supplied details do not give shaft dimensions or shift modes.

Skip it if you require confirmed shaft dimensions and three shift modes; Silscvtt's 30 Series gearbox lists both.

Consider this gearbox for a 30 Series 212cc build when its engine range and chain options match the kart. Buyers who need documented shaft dimensions or specific shift positions should treat those unspecified details as a fit boundary.

Listed on Amazon as: 30Series Forward Reverse Gear Box Kit 35Chain 12T 2300rpm

#8

8. GXYWADY 40 Series Gearbox

• Weight: 20.8 lb

Best for: 40 Series 530-Chain Replacement.

Why it ranks #8: A dedicated 40 Series option for 11–18HP engines, with a 3/4-inch keyed shaft and 12-tooth sprocket for 530 chain.

A 12-tooth sprocket for 530 chain distinguishes this GXYWADY 40 Series replacement, enabling a defined chain connection for listed go-kart and utility-vehicle applications. Its fitment covers 11–18HP engines, including Predator 420cc and Duromax 11HP-and-over engines, giving higher-output builds a specified gearbox option.

The 3/4-inch jackshaft with a 3/16-inch keyway provides a clear shaft interface to compare with the existing drivetrain, while the 12-tooth sprocket is listed for 530 chain. GXYWADY identifies 40 Series applications from 11HP to 18HP and names Predator 420cc and Duromax 11HP-and-over engines. The stated ratios are 1:2 forward and 1:2:6 reverse. These specifications make engine, shaft, and chain matching central to replacement planning.

Skip it if you have a 30 Series setup using #35 or #40/41/420 chain; maXpeedingrods' 30 Series kit lists those chain options.

Select this replacement for a 40 Series kart or utility vehicle whose engine, 3/4-inch keyed shaft, and 530 chain match the listing. Its 11–18HP application range is the important boundary for choosing it.

Listed on Amazon as: GXYWADY 40 Series Forward Reverse Gearbox Replacement for Go-Karts

#9

9. Leyuncot 40 Series Gearbox

• Weight: 23.1 lb

Best for: Predator 420cc 40 Series.

Why it ranks #9: Lists 11–18HP fitment, Predator 420cc applications, a 3/4-inch keyed shaft, and 530 chain with a 12-tooth sprocket.

A 3/4-inch intermediate shaft and 530 chain pairing make this Leyuncot 40 Series gearbox a specifically described replacement for larger go-kart drivetrains. Its listed 11–18HP range includes Predator 420cc and Duromax 11HP-and-above engines, helping builders identify a suitable application by engine and drivetrain dimensions.

The 3/4-inch shaft with a 3/16-inch keyway gives a concrete interface to compare with the existing setup, and the supplied 12-tooth sprocket uses 530 chain. Leyuncot lists forward ratio 1:2 and reverse ratio 1:2:6, indicating the two operating directions. Its 40 Series application range is 11–18HP, with Predator 420cc and Duromax 11HP-and-above engines specifically named. Matching series, shaft, and chain is essential to replacement planning.

Skip it if you run a 30 Series torque converter and #35 chain; GXYWADY's 2HP–13HP kit lists that setup.

Choose Leyuncot for a 40 Series kart or utility vehicle when the engine falls within its stated range and the 3/4-inch shaft and 530 chain match. Those drivetrain requirements are the decisive fit boundary.

Listed on Amazon as: 40 Series Forward Reverse Gearbox 11-18hp Fit for Predator 420CC 530 chain

#10

10. MOOTINGMOTO Transfer Gear Case

Best for: Vertical-Engine Shaft-Drive Conversions.

Why it ranks #10: Its stated fit is a CG-series 150–250cc vertical engine with a 6-spline input, making it less aligned with common small-engine kart setups.

A 6-spline female input and 20mm output shaft with universal joint distinguish this MOOTINGMOTO reverse gearbox, enabling a shaft-drive connection for listed vertical-engine applications. It is described for CG-series 150cc–250cc motorcycle engines and also as a reverse transfer case for 150cc–300cc quad or go-kart use.

The 6-spline female input and 190mm input length give installers specific connection details to compare with a vertical-engine drivetrain. A 20mm output shaft with universal joint identifies the other side of the transfer connection, which can guide shaft-layout planning. The listing describes CG-series 150cc–250cc motorcycle engines, while its additional description refers to 150cc, 200cc, 250cc, and 300cc applications. Confirm that the engine and shaft arrangement fall within the applicable description.

Skip it if you need a 30 Series gearbox with #35 chain; maXpeedingrods' kit lists those kart drivetrain specifications.

Consider this transfer case for a shaft-drive conversion using a compatible vertical engine and matching spline and output arrangement. Its listed engine applications differ from conventional 30 and 40 Series gearbox fitments, so drivetrain layout is the key boundary.

Listed on Amazon as: Transmission Reverse Gearbox, Go Kart Forward and Backward Converter Transfer Gear Case for ATV 150cc 200cc 250cc 300cc Engine Trike Motorcycle