Genuine Mazda 6-Speed Gearbox Secondary 4th Gear • P610-17-303A

Genuine Mazda P610-17-303A 6-Speed Gearbox Secondary 4th Gear

Replacement Genuine Mazda secondary fourth gear for Mazda MX-5 Mk3.5 and Mk3.75 / NC 2.0L models fitted with the later 6-speed manual transmission from 2009 to 2015, plus the supported Mazda RX-8 applications listed in the compatibility table.

This internal transmission component forms the selectable fourth-gear ratio within the manual gearbox. When fourth gear is selected, the synchroniser hub and sleeve engage the gear, allowing engine torque to pass through the transmission at the intended gear ratio.

The gear works together with the mainshaft, countershaft, synchroniser ring, 3rd/4th clutch hub and sleeve, selector fork, bearings and associated locking hardware. Accurate tooth form, engagement-dog geometry and synchroniser contact surfaces are essential for smooth gear selection and reliable torque transfer.

This listing supplies one Genuine Mazda secondary fourth gear. One P610-17-303A gear is required per applicable gearbox.

Replacement may be required where the original gear teeth, engagement dogs, synchroniser contact surface or internal bore have become worn, chipped, scored or otherwise damaged. Possible symptoms include difficulty selecting fourth gear, jumping out of fourth gear, grinding during engagement, abnormal transmission noise or metallic debris found in the gearbox oil.

• Part type: Secondary fourth gear / 4th gear
• Primary use: Provides the selectable fourth-gear ratio within the manual transmission
• Location: Internal 6-speed manual gearbox assembly
• MX-5 application: Later Mk3.5 and Mk3.75 / NC 2.0L 6-speed manual gearbox
• Additional application: Mazda RX-8 facelift / Series 2 6-speed manual gearbox
• Quantity per gearbox: One
• Quantity supplied: One gear
• Brand: Genuine Mazda
• Part No.: P610-17-303A
• Also referenced as: P61017303A
• Transmission restriction: 6-speed manual only
• MX-5 restriction: Later 2009–2015 gearbox specification
• Not suitable for: 5-speed manual or automatic transmission

Fitment advice: Confirm the gearbox type and production period before ordering. P610-17-303A is supported for the later 2009–2015 MX-5 NC 6-speed manual gearbox. Earlier pre-facelift NC transmissions can use different internal gears, selector components and clutch-hub assemblies even where the vehicle is also fitted with a 6-speed gearbox.

Other items to consider: When replacing this gear, you may also want to consider purchasing the fourth-gear synchroniser ring, 3rd/4th clutch hub and sleeve, 3rd/4th selector fork, shaft bearings, locking nuts, snap rings, oil seals and the correct manual transmission oil. All adjoining gears and engagement components should be inspected during dismantling.

Useful tools / consumables: Transmission removal equipment, hydraulic press, bearing splitters and pullers, circlip pliers, shaft-support fixtures, dial gauge, micrometer, calibrated torque wrench, clean assembly lubricant and the specified Mazda manual transmission oil.

Difficulty guide: DIY Difficulty: Specialist / Advanced. Replacement requires complete or substantial gearbox dismantling, removal of gears and bearings from the transmission shafts and accurate inspection of synchroniser clearances, shaft end-float and adjoining components. Professional gearbox-rebuilding experience and suitable press equipment are strongly recommended.

Why Genuine Mazda? Genuine Mazda transmission gears are manufactured to the original tooth profile, engagement-dog geometry, dimensions, hardness and surface-finish requirements. Using the correct OE gear helps retain proper meshing, synchroniser operation, gear engagement and compatibility with the original Mazda shafts and transmission components.

What’s in the box: One Genuine Mazda secondary fourth gear, part number P610-17-303A. Synchroniser rings, clutch hub, selector fork, bearings, shafts, locking hardware and transmission oil are not included.

Installation notes: Record shaft layout, component orientation, selective shims and clearances during dismantling. Inspect the mating counter gear, synchroniser ring, engagement sleeve, clutch hub, selector fork and bearings before fitting the replacement. Assemble using the applicable Mazda workshop procedure, replace specified single-use locking hardware and seals, verify shaft end-float and selector operation, and refill the gearbox with the correct specification and quantity of transmission oil.