Mercedes-Benz 724.2 (8G-DCT)

Mercedes-Benz's transverse eight-speed dual-clutch — in the current A-Class, CLA, GLA and GLB.

It replaced the 7G-DCT in the same cars, sometimes within one model year, and the two share a great deal: both are wet dual-clutches, so neither has the low-speed judder that defines the dry units elsewhere in this catalogue. A shudder from rest on either is a fault rather than a characteristic.

The ratio count is what changed and it is what people report. Eight gears in a compact car means frequent changing and hunting between the tall ones on a light throttle — behaviour, not failure, and best settled against another example of the same model.

Its genuine faults present electrically: a gear refused, a limp mode, a code naming a solenoid or a clutch position sensor. Nothing slips first, which is what distinguishes a mechatronic problem from clutch wear.

Fluid is a control question rather than a maintenance one. The oil serves both the clutches and the hydraulics that move them, so worn fluid makes the gearbox change badly long before it makes anything fail — and on a transmission this new that is the stage almost every example is at.