Getrag 6DCT250 (DPS6)

The six-speed dual-clutch gearbox Getrag built for small transverse cars, sold by Ford as PowerShift and by Renault as the DC4. It is the most notorious transmission of its generation, and unusually among the entries here, its reputation is deserved on the engineering rather than on how the cars were looked after.

Its clutches are dry, and everything below follows from that one decision. A dry clutch has no fluid to carry heat away from it, so every pull-away, every hill start and every crawl through traffic is heat going into a friction surface that can only shed it slowly. Ford's own gearbox oil here is a gear lubricant — under two litres of it, for the shafts and bearings — where a wet dual-clutch of the same size runs around seven litres circulating through the clutch packs themselves.

If your car is a Mondeo, S-Max, Galaxy or Kuga, this is probably not your gearbox. Ford applied the PowerShift name to two entirely different units: this dry one in the Fiesta, Focus and EcoSport, and the wet-clutch 6DCT450 in the larger cars. They share a badge and a supplier and almost nothing else, and advice written for one is close to useless for the other.

What an owner actually meets is a car that will not pull away smoothly. The complaints are consistent and well documented — shuddering from rest, hesitation, harsh or delayed engagement, a lurch as the clutch finally takes up, and in the worst cases a car that will not move at all after the control unit decides the clutches are too hot and disengages them to protect them. Behind that:

• Clutch wear well before any reasonable service life, with slippage appearing by around 100,000 km and often far sooner in city use.
• Leaking input shaft seals, which put gear oil onto a friction surface that is supposed to be dry. This is the failure that turns a merely marginal design into a broken car.
• Transmission control module failures, which produce the same symptoms as worn clutches and have to be told apart before anybody buys parts.
• Synchroniser wear, caused downstream by clutches that are not engaging cleanly rather than by anything the driver did.

The most useful thing to say to somebody whose Fiesta is juddering is that they did not cause it. Every other gearbox on this site rewards fluid changes and punishes neglect; this one has no service schedule that would have saved it. Ford faced class actions in the United States, Canada and Australia over exactly these failures, was fined ten million dollars by the Australian regulator for how it handled the complaints, and was under a United States Department of Justice fraud investigation from 2019. A judder here is a design being reached, not a maintenance history being paid for, and that changes what an owner should reasonably expect from a dealer.