Genuine Mazda 3rd / 4th Gear Selector Fork – 6-Speed Manual • P610-17-40Y

Genuine Mazda 3rd / 4th Gear Selector Fork – 6-Speed Manual

Replacement Genuine Mazda third- and fourth-gear selector fork for Mazda MX-5 Mk3.5 and Mk3.75 NC 2.0 Sport models fitted with the later six-speed manual gearbox.

The selector fork is installed inside the manual transmission and engages with the 3rd/4th synchroniser sleeve. Movement of the gear-selector mechanism slides the fork and synchroniser sleeve into the required position to select either third or fourth gear.

Wear, distortion or damage to the fork can prevent the synchroniser sleeve from moving fully or remaining correctly engaged. This may contribute to difficult gear selection, incomplete engagement or a transmission that disengages from gear.

One 3rd/4th selector fork is fitted per applicable gearbox. This listing supplies one Genuine Mazda fork.

Important gearbox restriction: This part is for the revised six-speed manual gearbox fitted to later Mk3.5 and Mk3.75 NC 2.0 Sport models. Earlier 2005–2009 Mk3 NC six-speed gearboxes use selector fork P601-17-40Y. Five-speed manual and automatic transmissions are excluded.

• Part type: 3rd / 4th gear selector fork
• Common names: Shift fork / gear-selection fork / synchroniser fork
• Mazda catalogue description: Fork, Shift (3rd & 4th)
• System: Six-speed manual transmission
• Installation position: Inside the gearbox change-control assembly
• Operating position: 3rd/4th synchroniser hub and sleeve
• Function: Moves the synchroniser sleeve to select third or fourth gear
• Transmission application: Later six-speed manual gearbox
• Quantity fitted per gearbox: 1
• Quantity supplied: 1 selector fork
• Selector rail included: No
• Synchroniser hub or sleeve included: No
• Baulk rings included: No
• Bearings or gears included: No
• Brand: Genuine Mazda
• Part No.: P610-17-40Y
• Compact reference: P6101740Y
• Earlier NC1 six-speed fork: P601-17-40Y – not interchangeable without confirmed gearbox application
• MX-5 fitment: Mk3.5 and Mk3.75 NC 2.0 Sport, six-speed manual
• Additional Mazda application: Applicable RX-8 six-speed manual gearboxes

Typical reasons for replacement:

• Difficulty selecting third or fourth gear
• Gear lever movement not fully engaging the selected gear
• Transmission disengaging from third or fourth gear
• Selector-fork contact pads worn or damaged
• Fork bent or distorted following internal gearbox failure
• Synchroniser hub or sleeve being replaced
• Gearbox dismantled for overhaul
• Internal debris or component failure damaging the fork

Quantity advice: One 3rd/4th selector fork is fitted per applicable six-speed gearbox. This listing supplies one fork.

Gearbox identification: Confirm that the vehicle has the later 2009–2015 six-speed manual transmission before ordering. The earlier Mk3 NC1 six-speed gearbox uses a different 3rd/4th selector fork.

Diagnostic advice: Poor third- or fourth-gear selection is not necessarily caused by the selector fork alone. Inspect the synchroniser sleeve, hub, baulk rings, gears, selector rail, detents, bearings and external gear-change mechanism during diagnosis.

Fork inspection: Check the fork for bending, cracking, excessive side clearance and wear at the surfaces contacting the synchroniser sleeve. Replace a fork that cannot maintain correct sleeve alignment.

Synchroniser inspection: Inspect the 3rd/4th synchroniser hub, sleeve and baulk rings for damaged teeth, glazing, scoring, excessive wear or restricted movement.

Gear inspection: Examine the third- and fourth-gear engagement teeth for rounding, impact damage or abnormal wear. A new selector fork will not correct damaged gear or synchroniser engagement teeth.

Selector-rail inspection: Confirm that the selector rail is straight and that its detent mechanism moves correctly. Check all retaining pins, clips and interlock components disturbed during dismantling.

Replacement advice: The gearbox must be removed and dismantled to replace this component. Record the position and orientation of the original fork and associated selector components before removal.

Assembly advice: Lubricate the fork contact surfaces and selector mechanism using the lubricant specified by Mazda. Confirm that the fork moves freely without binding and that the synchroniser sleeve engages both gears correctly before closing the gearbox casing.

Transmission-oil advice: Refill the gearbox with the correct specification and quantity of manual-transmission oil. Contaminated or unsuitable oil can adversely affect synchroniser operation and gear selection.

Other items to inspect: Check the 3rd/4th synchroniser assembly, selector rail, selector pins, shift detents, third and fourth gears, bearings, gearbox seals and drained transmission oil for metallic debris.

Useful tools / consumables: Vehicle lift or axle stands, transmission jack, gearbox pullers and press equipment, bearing separators, circlip pliers, measuring equipment, calibrated torque wrench, assembly lubricant, replacement seals and the specified manual-transmission oil.

Difficulty guide: DIY Difficulty: Advanced / Specialist. Replacement requires gearbox removal, complete or partial transmission dismantling, careful measurement and correct reassembly of the six-speed geartrain.

Why Genuine Mazda? Genuine Mazda selector forks match the original rail, synchroniser sleeve and gearbox geometry. Correct fork alignment and contact dimensions are essential for complete gear engagement and reliable synchroniser operation.

What’s in the box: One Genuine Mazda third- and fourth-gear selector fork, part number P610-17-40Y.

Installation notes: Remove and dismantle the transmission according to the applicable Mazda workshop procedure. Inspect the complete 3rd/4th gear-selection and synchroniser assembly before replacing the fork. Install the new component in the correct orientation, check selector-rail movement and confirm full engagement of third and fourth gears during bench testing. Reassemble the gearbox with new applicable seals, refill it with the specified oil and confirm correct gear selection before road use.