Fiat C635 (DDCT)

Fiat's six-speed transverse dual-clutch — the DDCT, which Alfa Romeo sells as TCT. The manual of the same designation has its own page, because it is a different machine wearing one name. In the Giulietta, MiTo, 500L, 500X, Tipo, Toro, Renegade, Compass and the Dodge Journey.

The DDCT is a DRY dual-clutch, and that single fact predicts its behaviour. A wet dual-clutch runs its clutches in oil, which carries heat away; a dry one has only air. So it is excellent once moving and 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 these clutches, because the transmission answers by slipping a clutch against the whole weight of the car with nowhere to put the heat. Use the brake, and the hill-hold, and let it engage. A clutch that has been held this way judders from rest and smells hot, and the juddering is the last stage rather than the first.

The other recurring failure is the TCM and its actuators — the gearbox is fine and the electronics that move it are not, producing a refusal to select, a limp mode, or a car that will not leave neutral. The symptom looks catastrophic and the gearbox is usually untouched.

It is not the Dualogic. The automated manual it replaced has one clutch, a hydraulic pump and an entirely different failure.