UNDERSTANDING THE DIFFERENCES BETWEEN A DRY AND WET DUAL CLUTCH TRANSMISSION

What is a Dual Clutch Transmission?

Otherwise known as a twin-clutch transmission, a dual clutch transmission offers performance, lightning-fast gear shifts as well as efficiency by using two separate clutches – one for odd-numbered gears and the other for even-numbered gears. The dual clutch system allows for the two clutches to work in tandem – pre-selecting the next gear even before the current gear is disengaged. Dual clutch transmissions can move from one gear to another, faster than that of any human. In VW and Audi Direct Shift Gearboxes (DSG), a gear changes from one to the next as fast as 0.008 seconds! 

The two main types of DCTs are wet dual clutch and dry dual clutch systems, which differ in how the clutches are lubricated and cooled.

Wet Dual Clutch Transmission

A wet dual clutch transmission, simply put, operates with the clutches submerged in oil. The clutch packs are bathed in oil to provide constant lubrication and to absorb heat while in operation (cooling). This type of DCT is used in heavy-duty and high-performance applications where the transmission is exposed to high levels of stress and load due to torque and rapid shifting.

Examples are:

• Porsche PDK (Porsche Doppelkupplungsgetriebe)
  RAVENOL PDK FLUID
• Volkswagen DSG (Direct Shift Gearbox) – the wet clutch version is found in high performance models such as the Golf GTI and Golf R – namely, the DQ250 and DQ381
  RAVENOL DCT/DSG GETRIEBE FLUID & RAVENOL DCT-DSG LV FLUID
• Nissan R35 GT-R GR6 Dual Clutch Transmission
  RAVENOL DCT GT-R FLUID

Dry Dual Clutch Transmission

A dry dual clutch transmission’s clutches do not operate with any fluid interaction (the oil does not lubricate the clutches). This means that the entire system is simpler and lighter, which results in lower maintenance costs and better fuel economy. These gearboxes are best suited toward vehicles with moderate torque output, which are not subjected to high levels of stress.

Examples are:

• Fiat Dualogic
• Volkswagen DSG (Direct Shift Gearbox) – VW also offers a dry version of the DSG in its smaller, less powerful vehicles like the Polo
• Ford Powershift

Dry Dual Clutch Transmissions tend to use manual transmission fluids such as:

• RAVENOL MTF-2 SAE 75W-80
• RAVENOL MTF-3 SAE 75W

Key Differences Between Dry & Wet DCT’s

Mechatronics & Hydraulic Actuators

The Mechatronics Unit in VAG Cars

In Volkswagen and Audi Group (VAG) vehicles, the mechatronics unit is a crucial component of the DSG system. This unit integrates both electronic and hydraulic control systems, allowing for precise management of gear changes, clutch engagement, and overall transmission operation. The mechatronics unit ensures smooth and rapid gear shifts, contributing to the performance and efficiency of the vehicle.

Recommended Ravenol Product:

To maintain optimal performance of the mechatronics unit, RAVENOL SSF (Special Servolenkung Fluid) is recommended. This fluid provides excellent lubrication and pressure stability, ensuring the reliable operation of the hydraulic components within the mechatronics system.

Fiat’s Hydraulic Actuator Gearboxes

Fiat utilises hydraulic actuators in some of its gearboxes, such as the Dualogic system. These actuators control gear shifts and clutch operations hydraulically, providing smooth and efficient transmission performance.

Recommended Ravenol Product:

For Fiat’s hydraulic actuator gearboxes, RAVENOL GHA-F Fluid is specifically formulated to meet the unique requirements of these systems. It ensures optimal hydraulic performance, reliability, and longevity of the actuator components.

Before replacing any fluids, we highly recommend using our OIL FINDER to confirm the correct oil for your vehicle. Alternatively, you can use our ASK AN EXPERT feature on our website to get a personalised recommendation from one of our technical staff.

The decision between wet and dry dual clutch transmissions largely depends on their intended use. Wet DCTs are designed for high-performance vehicles where durability, heat management, and smooth gear shifts are essential. In contrast, dry DCTs focus on simplicity, efficiency, and affordability, making them ideal for smaller, everyday cars.

Whether you’re behind the wheel of a Porsche 911 with a wet PDK system or a Ford Focus with a dry Powershift, understanding the differences between these transmissions enhances your appreciation for the engineering behind modern automotive technology. And with Ravenol’s selection of Dual Clutch Transmission Fluids, you can ensure that your transmission—whether wet or dry—remains in peak condition for years to come!