ISUZU NPR 4HE1 Clutch Slave Cylinder 8-97039709-1 OEM Fit

The Clutch Slave Cylinder with OEM numbers 8-97039709-1 and 8970397091 is a verified direct-fit replacement for ISUZU NPR / NQR71 / NQR75 series trucks equipped with the 4HE1 / 4HE1T engine and MM6U / MZZ6U / MZZ6 transmission. This slave cylinder is the actuator of the clutch hydraulic system, responsible for converting hydraulic pressure from the clutch master cylinder into mechanical force that pushes the release fork and release bearing, disengaging and engaging the clutch.

The clutch slave cylinder is mounted on the side of the transmission, with its push rod connected to the clutch release fork. When the clutch pedal is depressed, the master cylinder generates hydraulic pressure, which is transmitted through the hydraulic line to the slave cylinder, pushing the slave cylinder piston and push rod outward. The push rod pushes the release fork, which in turn pushes the release bearing against the diaphragm spring, separating the clutch disc from the flywheel and cutting off power flow.

When the pedal is released, the hydraulic pressure is released, and the return spring brings the release fork and slave cylinder piston back to their rest positions, re-engaging the clutch. The 8-97039709-1 features a cast iron housing and 20.6 mm piston, providing stable thrust output and reliable sealing performance in the clutch hydraulic system of ISUZU medium-duty commercial vehicles.

Replace the slave cylinder when any of these symptoms appear:

• Spongy, sinking, or abnormally long clutch pedal travel — internal seal wear causes fluid bypass in the slave cylinder.
• Visible clutch fluid leakage at the transmission side or slave cylinder dust boot — piston seal failure.
• Difficulty shifting gears or gear grinding — insufficient slave cylinder thrust prevents full clutch disengagement.
• Clutch pedal does not return or returns slowly — piston binding in the slave cylinder.
• Insufficient push rod travel or push rod disengagement — internal failure or push rod connection failure.

1. 1Preparation: Disconnect the battery negative terminal. Drain the clutch fluid reservoir with a syringe. Clean the slave cylinder and line connections.
2. 2Removal: Disconnect the hydraulic line from the slave cylinder. Remove the slave cylinder mounting bolts. Detach the push rod from the release fork. Withdraw the old slave cylinder.
3. 3Inspection: Inspect the transmission mounting surface for damage. Check the hydraulic line for corrosion or blockage. Inspect the release fork and release bearing.
4. 4Installation: Install the new slave cylinder onto the transmission and torque the mounting bolts to specification. Connect the hydraulic line. Attach the push rod to the release fork.
5. 5Filling & Bleeding: Fill the reservoir with fresh DOT 3 or DOT 4 brake fluid. Thoroughly bleed the clutch hydraulic system (expel air from the slave cylinder bleeder screw).
6. 6Pedal Test: Pump the clutch pedal several times to verify a firm pedal. Check for leaks at all connections.
7. 7Road Test: Perform a road test at low speed to confirm smooth gear engagement and complete clutch disengagement.

• Every 10,000 km: Check clutch fluid level and condition. Inspect slave cylinder and lines for leaks.
• Every 40,000–50,000 km: Check for complete clutch disengagement. Check slave cylinder push rod travel.
• Approx. 200,000 km (ISUZU recommendation): Inspect/replace the slave cylinder and inspect the master cylinder at the same time.
• When a spongy pedal or hard shifting is detected: Inspect the slave cylinder and hydraulic system immediately.

• Standard Packaging: Anti-rust oil + VCI film + neutral carton (19.5 × 9 × 5 cm).
• Custom Packaging: Neutral box, color box, or customer-branded packaging.
• Suitable For: Clutch/transmission repair shops, ISUZU parts distributors, fleet maintenance centers.
• Supply Capacity: Stable batch supply with batch-level quality reports available.
• MOQ: Small quantities accepted (quantity discounts available).