DSG in House Gearbox & Clutch Repairs

What is a double-clutch transmission DSG – Direct Shift Gearbox/S-Tronic?

The DCT consists of two independent sub-transmissions positioned in a single transmission housing. Each sub-transmission is constructed like a manual transmission in terms of function. Consequently, each sub-transmission is assigned its own clutch. Dry and wet versions of the clutches are possible, depending on the engine torque and mounting space.

While driving, all the processes of a gear shift are regulated automatically. A control unit relays commands to either an electrohydraulic or electromechanical actuating mechanism. This enables the clutches and gear shift forks to perform their work within a precisely defined time window.

One sub-transmission is therefore always connected to the engine in a non-positive connection. In the other sub-transmission, the next gear is preselected and is ready to be requested. In driving mode, the clutches are then actuated alternately within a matter of milliseconds. For the driver, this means, among other things, greater driving comfort due to barely noticeable interruptions of tractive power when accelerating.

The DCT is available with a wet or dry double clutch. Vehicle manufacturers decide between these systems based mainly on mounting space, torque capacity and cost-effectiveness.

Wet double clutches require little mounting space and can transfer higher torques because of their good heat dissipation. However, drag losses in the oil experienced by the clutch and the pump performance lead to a reduction in efficiency.

The dry double clutch requires slightly more mounting space, but it works more efficiently as no oil is being moved in the clutch area. Frictional heat needs to be dissipated through the air, which is a poorer heat conductor.