Full AW30-40LE (A340 Series) Transmission Workshop Manual. Includes detailed repair procedures, hydraulic flow charts, solenoid testing, and rebuild specifications. Essential guide for Isuzu, Toyota, and Mitsubishi owners.
| Feature | Specification |
| Transmission Type | 4-Speed Automatic, Electronically Controlled (ECT) |
| Manufacturer | Aisin Warner (Japan) |
| Input Torque (Max) | ~350 lb-ft (approx. 450–480 Nm) |
| Case Material | Die-cast Aluminum |
| Weight (Approx.) | 175–190 lbs (79–86 kg) including fluid |
| Fluid Type | Toyota ATF Type T-IV / Dexron III (model dependent) |
| Fluid Capacity (Service) | 4.3 – 5.0 quarts (approx. 4.1 – 4.7 liters) |
| Fluid Capacity (Dry/Total) | 10.1 – 11.5 quarts (approx. 9.5 – 10.9 liters) |
| Stall Torque Ratio | 1.85:1 to 2.1:1 (varies by torque converter) |
| Password for PDF: truckfixdiagn.com | |
| Isuzu TF Series AW30-40LE Transmission Workshop Manual | Download |
| Isuzu D-Max Transmission Control System | Download |
| Isuzu D-Max On Vehicle Service 4087 | Download |
| Isuzu D-Max Unit Repair 4137 | Download |
| Isuzu D-Max Transfer Case | Download |
Diagnostic Summary Table
| Symptom | Probable Cause | Diagnostic Action |
| No 4th Gear (Overdrive) | Bad S2 Solenoid or O/D Switch | Check solenoid resistance / Check O/D button |
| Vibration at 50 mph | Torque Converter Shudder | Test by lightly touching brakes while driving |
| Erratic Shifting / Limp Mode | Shift Solenoid Failure | Scan for DTC codes (e.g., P0753, P0758) |
| RPM Flare on Shifts | Worn Valve Body Bores | Inspect line pressure and fluid condition |
| Hard Shifting (Mechanical) | Misadjusted Throttle Cable | Adjust cable at the throttle body |
Common AW30-40LE (A340) Transmission Problems
1. Shift Solenoid Failure (Most Common)
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The Cause: The S1, S2, or Lock-up solenoids can fail electrically (internal coil break) or become clogged with debris.
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The Symptom: The transmission gets stuck in a single gear (Limp Mode), fails to upshift, or experiences erratic shifting behavior.
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The Fix: Testing the resistance of the solenoids. Fortunately, these can be replaced by simply dropping the transmission pan without removing the entire gearbox.
2. Valve Body Wear & Internal Leaks
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The Cause: Over time, the steel valves wear out the aluminum bores in the valve body.
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The Symptom: Soft or "lazy" shifts, flares (RPM spike) during gear changes, or the "Check Trans" light flashing on the dashboard.
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The Fix: Installing a valve body recalibration kit (e.g., Sonnax or TransGo) or replacing the valve body assembly.
3. Torque Converter Shudder
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The Cause: The lock-up clutch inside the torque converter begins to slip or the friction material becomes glazed.
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The Symptom: A vibration or "shudder" that feels like driving over rumble strips, typically occurring at constant speeds between 40–55 mph (65–90 km/h).
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The Fix: A full transmission fluid flush often helps. If the shudder persists, the torque converter must be replaced.
4. Overheating in Heavy-Duty Use
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The Cause: Restricted flow through the factory radiator-based cooler, especially during towing or off-roading.
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The Symptom: Dark, burnt-smelling fluid, slipping gears when hot, and accelerated wear of clutches and seals.
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The Fix: Installing an auxiliary external transmission cooler (highly recommended for Isuzu D-Max and Toyota Hilux owners).
5. Worn Throttle Cable (Kick-down Cable)
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The Cause: On older versions of this transmission, a mechanical cable controls line pressure based on throttle position. The cable can stretch or snap.
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The Symptom: Harsh shifting or, conversely, early/soft shifts that cause the clutches to slip and burn out.
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The Fix: Checking and adjusting the cable tension according to the factory workshop manual.
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