BENTLEY FLYING Spur Gearbox 8HP-90 QGS W12

Bentley Flying Spur equipped with the 6.0L W12 engine utilizes the high-torque ZF 8HP90 automatic transmission. The “QGS” designation refers to the specific internal calibration or build code for the unit used in this application.

1. Technical Specifications (ZF 8HP90)

The 8HP90 is ZF’s most heavy-duty 8-speed automatic, specifically engineered to handle the massive torque output of W12 and V12 engines.

• Torque Capacity: Rated for up to 1,000 Nm (738 lb-ft), providing a significant safety margin for the W12’s 800–900 Nm output.

• Block Shifting: One of the key features of the Flying Spur’s 8HP90 is its ability to skip gears (e.g., shifting from 8th directly to 3rd) during rapid acceleration, reducing shift lag.

• Mechanical Shift Time: Approximately 600ms, allowing for a balance of luxury smoothness and performance response.

• Weight: Approximately 95–100 kg, including fluid.

2. Gear Ratios (QGS Calibration)

3. Service & Maintenance

Despite Bentley’s “Fill for Life” claims on some earlier models, ZF recommends servicing the 8HP90 every 60,000 to 100,000 km (approx. 40k–60k miles) or every 8 years, especially in high-performance W12 applications.

• Fluid Type: ZF LifeGuard 8 (Green/Blue fluid). Using the wrong fluid (like LifeGuard 6) can cause solenoid failure and slipping.

• Service Kit: The filter is integrated into the plastic oil pan (sump). You must replace the entire pan assembly when changing the fluid.

  • OEM Pan Part Number: 0D6398359B (Verify via VIN).

• Fluid Capacity: Total system holds ~9 liters; a standard service drain and fill typically uses 5–7 liters.

4. Common Diagnostic Issues

• Mechatronic Faults: If the unit is experiencing “harsh shifts” from 2nd to 1st or 3rd to 2nd, it often requires a software adaptation or a reset of the “learning” values via a Bentley-specific diagnostic tool.

• Input Shaft Seal: In high-mileage units, the seal between the W12 engine and the 8HP90 can develop leaks. Due to the tight packaging of the Flying Spur, this usually requires an engine/gearbox drop to repair.

5. Identification for Inventory

If you are sourcing or selling this specific unit, look for the Green I.D. Plate on the side of the gearbox housing. It will list:

• ZF Part Number: Likely starts with 1091 (e.g., 1091 042 031).

• Serial Number: Unique to the unit.

• Bentley Code: QGS or similar 3-letter code.