Manual Transmission Assembly 8980676800 / 8-98067680-0 For ISUZU NPR75 NQR90 4HK1 4JJ1 4HF1 — MYY6S 6-Speed, Aluminum Case, Overdrive 6th, 419 N·m

The Manual Transmission Assembly with OEM references 8980676800 / 8-98067680-0 (and factory references 8-98067680-1, 8-98067656-0, 1701010-ME25A) is a verified replacement MYY6S 6-speed manual gearbox for ISUZU NPR75, NQR90, and related N-Series commercial trucks equipped with 4HK1 (5.2L), 4JJ1 (3.0L), 4HF1, and 4HG1 diesel engines. This is the complete transmission assembly — the full gearbox unit that transmits engine torque to the rear axle through the selected gear ratio, including the aluminum alloy case, gear train, synchronizers, and shift mechanism.

The MYY6S is a 6-speed overdrive manual transmission with a torque capacity of up to 419 N·m, matched to the 4HK1's commercial duty output. The gearbox case is manufactured from high-strength aluminum alloy, reducing weight without sacrificing structural rigidity. The 6th gear is an overdrive ratio, reducing engine RPM at highway speed for improved fuel economy. The unit is fully compliant with Euro 4 and Euro 5 emission standards and is designed for minimal maintenance with a reference service life of up to 1,000,000 km through thermally treated gears and shafts.

This is the MYY6S transmission — a 6-speed manual with overdrive 6th gear. It is not the MYY5T (5-speed) or other ISUZU manual gearbox variants. The transmission model must match the vehicle's original configuration for correct gear ratios, bellhousing pattern, and shift linkage. Confirm the original transmission code before ordering.

This listing covers the complete gearbox assembly. The clutch, release bearing, and flywheel are not included unless explicitly stated. The unit is supplied dry (without gear oil) in standard export configuration. Confirm the package scope and oil fill requirement at inquiry.

The primary OEM reference 8980676800 / 8-98067680-0 is interchangeable with 8980012130 and 8-98067656-0 in aftermarket catalogs. The 8-98067680-1 suffix variant is also referenced. Confirm the original unit's marking or VIN to ensure the correct replacement reference is supplied.

• Transmission Model & Configuration Verified: MYY6S, 6-speed manual, overdrive 6th gear — confirmed across multiple supplier catalogs and technical listings. One source describes it as a "6-speed manual transmission assembly" for 4HK1/4JJ1/4KH1/4HF1/4HG1 engines.
• Torque Capacity Verified: Up to 419 N·m — confirmed by technical data for the MYY6S matched to the 4HK1 5.2L diesel.
• Material Verified: Aluminum alloy case — confirmed by multiple supplier listings describing the gearbox housing as aluminum for weight reduction.
• Service Life & Emission Compliance Verified: Up to 1,000,000 km through thermally treated gears and shafts; Euro 4 and Euro 5 compliant — confirmed by technical product data.
• Vehicle & Engine Coverage Verified: ISUZU NPR75, NQR90 — confirmed by multiple catalogs. 4HK1, 4JJ1, 4HF1, 4HG1 engines — confirmed by MAMUR and GUANGLIAN supplier application data.
• Cross-Reference Density Verified: 8980676800, 8-98067680-0, 8-98067680-1, 8-98067656-0, 8980012130, 1701010-ME25A are consistently grouped as interchangeable or related references across multiple catalogs.
• Factory / Alternate References Verified: 1701010-ME25A (QINGLING OEM), 8981814960 (alternate catalog reference), 8-98067656-0 (related variant).
• Brand & Supply Reference: MAMUR brand available; MOQ 1 PCS; delivery 5–30 days after deposit; MAMUR packaging — confirmed by supplier data.
• Gear Oil Specification and Fill Quantity NOT Publicly Published: The accessible supplier data does not specify the recommended gear oil grade or fill volume for the MYY6S. Confirm against the ISUZU NPR75 workshop manual before commissioning the transmission.

• Difficulty engaging or selecting gears: Worn synchronizer rings, bent shift forks, or a damaged shift mechanism prevent smooth gear selection — the most common symptom of an aging MYY6S gearbox.
• Gear jump-out / popping out of gear: Worn detent springs, damaged shift forks, or excessive bearing play allow the transmission to disengage unexpectedly under load or vibration.
• Transmission whine or growl that changes with speed: Worn bearings or gear tooth wear produce continuous noise that varies with vehicle speed and may change pitch under acceleration or deceleration.
• Grinding or crunching during gear changes: Worn synchronizers or a dragging clutch (not disengaging fully) cause gear clash during upshifts or downshifts.
• Oil leak from the transmission case or seals: Cracked aluminum case, failed input/output shaft seals, or a damaged pan gasket allow gear oil to escape, leading to lubrication starvation.
• Complete loss of drive in one or more gears: Broken gear teeth, a failed shift fork, or a shattered synchronizer can leave the vehicle unable to move in certain gears or entirely.

• Transmission code is the first check: This is the MYY6S (6-speed overdrive). Confirm the original gearbox code before ordering — the MYY5T (5-speed) and other ISUZU manual transmissions use different gear ratios and bellhousing configurations. Do not substitute without verifying the original transmission code.
• Clutch and release bearing are separate: This listing covers the complete gearbox assembly only. The clutch disc, pressure plate, and release bearing are separately supplied and must be ordered as required.
• Gear oil fill: The transmission is supplied dry in standard export configuration. Confirm the correct gear oil grade and fill quantity against the ISUZU NPR75 workshop manual before commissioning.
• Replacement reference mapping: 8980676800, 8980012130, and 8-98067656-0 are treated as interchangeable in the aftermarket. Confirm the original unit's marking where possible, and ensure the supplied reference matches the ordered reference.

1. Confirm the required part first: Verify the original transmission is the MYY6S and that the replacement's bellhousing pattern, input shaft spline, and output shaft configuration match the vehicle. Confirm whether a clutch and release bearing are also required.
2. Remove the old transmission: Support the gearbox with a transmission jack. Disconnect the driveshaft, shift linkage, clutch hydraulic line, and any electrical connectors. Do not let the gearbox hang on the input shaft — this can damage the clutch and release bearing.
3. Inspect the clutch and flywheel: With the transmission removed, inspect the clutch disc, pressure plate, release bearing, and flywheel surface. Replace worn components before installing the new gearbox — reusing a worn clutch with a new transmission is a false economy.
4. Install the new transmission: Mate the gearbox to the engine, ensuring the input shaft splines engage the clutch disc smoothly. Do not force the transmission into place — misalignment can damage the input shaft or clutch.
5. Reconnect the driveline: Reconnect the driveshaft, shift linkage, clutch hydraulic line, and electrical connectors. Torque all fasteners to the workshop manual specification.
6. Fill with gear oil: Fill the transmission with the ISUZU-recommended gear oil to the specified level. Confirm the oil grade and fill quantity against the workshop manual — under-filling or using the wrong grade will cause premature bearing and gear wear.
7. Test operation: With the engine running and the vehicle stationary, operate the gear lever through all gears. Confirm smooth engagement and no abnormal noise. Road-test through a range of load conditions, checking for smooth shifting and no jump-out.

• Change transmission gear oil according to the ISUZU NPR75/NQR90 schedule (typically every 40,000–60,000 km, or more frequently in severe duty). Degraded oil accelerates synchronizer and bearing wear.
• Inspect the transmission for oil leaks at every service — early detection of seal failure prevents lubrication starvation.
• Monitor shift quality at every service — difficulty engaging gears or gear jump-out are early warning signs of synchronizer or shift fork wear.
• Avoid aggressive shifting and overloading — shock loads accelerate gear and bearing fatigue.

• Standard packing: MAMUR packaging (reference); neutral or customer-branded packaging available. Heavy-duty export crate/pallet recommended for this assembly.
• Package contents: 1 × MYY6S Manual Transmission Assembly. Clutch, release bearing, gear oil, and mounting hardware are not included unless explicitly stated — confirm exact package contents at inquiry.
• Set options: Transmission assembly only (standard) / transmission + clutch kit (where available) — specify at inquiry.
• Minimum order: 1 PCS (MAMUR reference); bulk quantity pricing available.
• Suitable for: ISUZU NPR75 / NQR90 driveline repair shops, commercial truck fleet maintenance departments, gearbox rebuilders, spare parts distributors, and export wholesalers.