Dual-clutch (DCT / DSG)

The architecture, for the cars whose specification says only dual-clutch or DSG and names no unit.

It is two manual gearboxes in one case, one holding the odd gears and one the even, each with its own clutch. While you are in third, fourth is already engaged on the other shaft and waiting — which is why the change is fast, and why there is no torque converter to smooth anything.

⚑ The one question that decides everything about a dual-clutch is whether it is DRY or WET, and almost nothing in a specification says which.

• A dry DCT's clutches run in air. There is nothing to carry heat away, so it is at its least happy exactly where a torque-converter automatic is most comfortable: creeping in traffic, and holding station on a hill. Holding the car on an incline with the throttle is what destroys the clutches — the brake and the hill-hold cost nothing. A judder from rest is the late stage, not the first.
• A wet DCT's clutches run in oil, which carries the heat away. That judder is not a characteristic of one — so on a wet unit the same symptom is a genuine fault rather than the design meeting a driving habit.

Advice about one therefore misdirects on the other, and both are sold under the same names. Volkswagen's DQ200 is dry and its DQ250 and DQ500 are wet; all three are DSG. Hyundai's 7DCT is dry and its 8DCT is wet. Establish which you have before reading anything else.

On both kinds the expensive failure is the mechatronic unit, and it presents electrically: a gear refused, a limp mode, a code naming a solenoid or a clutch position sensor. Nothing slips first, which is what separates it from clutch wear.

On a wet unit the fluid is a control question rather than maintenance — the oil serves the clutches and the hydraulics that move them, so worn fluid makes the gearbox change badly long before it makes anything fail.

A dual-clutch is not an automated manual. That has one clutch and a robot, pauses on every change, and is a different repair; it has its own page here.