For the Porsche Cayenne (958 / 92A), the A55.04 is the factory code for the Aisin 8-speed Tiptronic S automatic transmission paired with the 3.6L V6 (VR6) gasoline engine. Unlike the Macan’s dual-clutch PDK, the Cayenne uses a heavy-duty torque converter automatic to handle towing and off-road loads.

1.Tchnical Specifications

The A55.04 is a variant of the Aisin 0C8 transmission family, also found in the Volkswagen Touareg and Audi Q7.

• Transmission Speed: 8-Speed Tiptronic S.

• Engine Match: 3.6L V6 (Naturally Aspirated), 300 hp / 295 lb-ft (Engine codes: M55.02 / CEYA).

• Drive System: Porsche Traction Management (PTM) active all-wheel drive with an electronically controlled multi-plate clutch.

• Gearbox Codes: You may also see the 3-letter mechanical code MXM or NUA stamped on the casing alongside A55.04.

2. 2026 Market Value

By 2026, many 958.1 and 958.2 Cayennes are reaching high mileage. The Aisin units are robust, but second-hand demand is high for high-mileage replacements.

3. Maintenance: The “Lifetime” Fluid Correction

While Porsche originally marketed this as a “lifetime” fill, specialists in 2026 recommend a service every 60,000 – 80,000 miles to prevent harsh shifting.

• Fluid Type: ATF T-WS (Spec: AW-1 / Porsche P/N: 000 043 306 24).

• Dry Fill Capacity: $10\text{–}12\text{ Liters}$.

• Drain & Filter Change: Usually requires $7\text{–}9\text{ Liters}$.

• Filter Part Number: 958-325-435-00.

4. Common Failure: The Valve Body

The most frequent issue with the A55.04 isn’t the gears themselves, but the internal valve body.

• Symptoms: Harsh downshifts (especially from 3rd to 2nd) or “clunking” when shifting into Drive or Reverse when the car is hot.

• The 2026 Fix: Rather than replacing the whole gearbox, many owners now opt for a Valve Body Rebuild or replacement (approx. $800 – $1,200), which restores factory shifting smoothness without removing the transmission from the car.

5. Installation & The “Transfer Case” Warning

The A55.04 gearbox is physically bolted to the Transfer Case.

• Important: If you are experiencing a “shudder” or “jerking” during acceleration at low speeds, it is almost certainly the Transfer Case, not the A55.04 gearbox.

• Coding: Swapping the transmission requires “adapting” the transmission control module (TCM) to the car’s VIN using PIWIS III. If you don’t do this, the car may stay in “Limp Mode” (locked in 3rd gear).