8-speed DSG transmission for Audi A3 40 TFSIe, model year 2021, code UJX

Transmission Type: 6-Speed S-tronic (Triple-Clutch Hybrid) Part Number: 0DD300040L (0DD 300 040 L) Model Year: 2021–Present Application: 1.4 TFSI Plug-in Hybrid (PHEV)

The UJX is a specialized version of the DQ400e transmission, specifically engineered for the Audi A3 Sportback 40 TFSIe (Type 8Y). While often colloquially referred to as an “8-speed” due to confusion with Audi’s torque-converter Tiptronic units, the UJX is actually a 6-speed dual-clutch system that incorporates a third clutch (K0) to manage the integration of the electric motor.

Technical Specifications

• Transmission Family: DQ400e (Generation 2).

• Gearbox Architecture: 6-Speed transverse dual-clutch with integrated electric motor (HEM).

• Electric Motor Power: Integrated 80 kW (approx. 109 PS) permanent-magnet synchronous motor.

• Torque Capacity: Combined system output of 350 Nm (250 Nm from the 1.4L engine + electric boost).

• Clutch System: * K1 & K2: Standard dual-clutch for gear selection.

  • K0: Disconnection clutch that decouples the combustion engine for pure electric driving (EV Mode).

Key Performance Features

• Hybrid Synergy: The UJX code is optimized for the 2021+ “8Y” chassis electronics. It allows for seamless transitions between pure electric, hybrid, and “GTE/S” performance modes.

• Recuperation: The internal electric motor acts as a generator during braking, sending up to 40 kW of energy back to the high-voltage battery.

• Start-Stop Efficiency: Because the electric motor handles the initial launch, the “creep” behavior is significantly smoother than traditional DSG units, reducing mechanical wear on the friction plates.

Professional Installation & High-Voltage Safety

Warning: The UJX contains a high-voltage electric motor. Installation should only be performed by technicians certified in High-Voltage (HV) systems.

1. De-energizing the System: Before removal or installation, the vehicle’s high-voltage system must be powered down using the maintenance plug (typically located in the engine bay) and verified with a voltmeter.

2. Component Protection: The Transmission Control Unit (TCU) is part of the Audi Immobilizer system. A replacement UJX unit will require an online connection to Audi ODIS to clear “Component Protection” and “Software Version Management” (SVM) coding to match the vehicle’s 40 TFSIe power map.

3. Cooling System: This transmission features a dual cooling circuit—one for the gear oil and a separate low-temperature water circuit for the electric motor. Both must be bled of air using a vacuum filling tool to prevent inverter or motor overheating.

4. Fluid Specification: Requires G 055 529 A2 (S-tronic Fluid). Despite being a hybrid, the mechanical gear-set still requires periodic fluid changes (typically every 60,000 km) to maintain shift quality.

Inventory Note: The UJX is the modern replacement for older hybrid codes like QRE or SAY. It is highly sought after for 2021+ A3 and VW Golf 8 GTE repairs.