PORSCHE 911 991 Carrera 4 GTS Front Axle Differential

In 2026, the Front Axle Differential (Final Drive) for the Porsche 911 (991) Carrera 4 GTS is a critical component of the PTM (Porsche Traction Management) system. Whether you have a 991.1 (3.8L) or a 991.2 (3.0L Turbo), the front differential is responsible for the lightning-fast torque distribution that gives the “4 GTS” its signature grip.

1. Technical Identification

The 991 Carrera 4 GTS uses an electronically controlled, water-cooled multi-plate clutch system integrated with the front differential.

• Part Number (Common): 991-349-010-06 (The part number often ends in a suffix like AX or BX depending on the specific revision and gear ratio).

• Compatibility: While the 991.1 and 991.2 differentials are physically similar, the clutch control software and internal gear ratios can differ. Always verify the fitment using your VIN to ensure the front and rear ratios match perfectly.

• Cooling: On the GTS models, the differential is often connected to the vehicle’s coolant circuit to maintain optimal operating temperatures during spirited driving.

3. Common Signs of Failure

If you are searching for this part, you may be experiencing one of the following “991-specific” issues:

• “AWD System Failure” Message: Often caused by the internal electromagnetic actuator or a failure in the multi-plate clutch.

• Binding/Shuddering: If the car “hops” or vibrates during tight, low-speed turns (like in a parking lot), the internal clutches may be worn or the fluid may be contaminated.

• Leaking Seals: The input shaft and side-axle seals are known to weep over time. In 2026, many owners choose to reseal the unit rather than replace the entire differential if the gears are still healthy.

4. 2026 Maintenance Tip: The “Fluid Service”

Many 991.1 and 991.2 models are now 7–12 years old. Porsche originally listed the front diff fluid as “lifetime,” but enthusiasts and specialists now recommend:

1. Changing the Fluid: Every 60,000 miles (100,000 km) or 6 years.

2. Calibrating the Clutch: After a fluid change, a PIWIS III/IV diagnostic tool should be used to perform a “clutch calibration” to ensure the PTM system knows the exact bite point of the plates.

5. Installation Notes

• Weight: The unit is heavy and positioned tightly between the front suspension components. Professional installation typically takes 4–6 hours.

• Drive Shafts: When replacing the differential, it is the best time to inspect the CV boots on the front drive shafts, as they must be disconnected during the process.