Aisin TF-60SN (09G)

Aisin's six-speed automatic for transverse front-wheel-drive cars, and the first of its kind anywhere — six ratios in a case that had to fit the space a five-speed occupied, using a Lepelletier gearset to get there with fewer parts rather than more. It has been in production since 2003 and is one of the most widely fitted automatics in Europe.

The single most useful thing to know about it is that it is not a DSG. Volkswagen, Audi, SEAT and Škoda fitted this gearbox as 09G alongside their own dual-clutch units, and an owner who has been told "it's the VW automatic, they're all trouble" is being told something about a different machine. This one is a conventional torque-converter automatic bought in from Japan: it has no clutch packs to wear out, no mechatronic unit in the sense the DQ250 and DQ200 have one, and none of their characteristic failures. If your car has a torque converter, the DSG advice does not apply to you.

It also wears at least four names, which is why owners of very different cars end up reading about the same gearbox. Aisin calls it the TF-60SN. Volkswagen calls it 09G, with 09K and 09M as the higher-torque and all-wheel-drive derivatives of the same design rather than separate gearboxes. BMW and Mini call it 6F21WA, and it is the six-speed automatic in the Mini hatch, Clubman, Convertible and Countryman, in the BMW X1 and in the three-cylinder 2 Series Active Tourer. A repair described for one is a repair for all of them.

What actually goes wrong starts at the torque converter, and it starts early. The lock-up clutch is run deliberately slipping to smooth the drive, and a clutch that is slipping is a clutch that is wearing — the friction material it sheds goes into the fluid, and the fluid goes everywhere. That single mechanism is upstream of most of the list below, which is why fluid condition matters more here than the absence of a factory service interval suggests. A change on the order of every 60,000 km is what separates the units that reach high mileage from the ones that do not.

What the trade replaces, roughly in the order it arrives:

• Valve body solenoids and valves, worn or clogged by exactly the debris described above. This is the commonest repair on the unit and it usually announces itself as a ratio fault code rather than as a noise.
• The heat exchanger, which silts up with the same material and then stops cooling the fluid that is carrying it — a loop that accelerates itself.
• The K2 and C2 clutch packages, where worn parts leak and clutch-pack pressure falls away.
• Oil pump bushings, which wear under shaft vibration and cost pressure everywhere downstream. The trade replaces them at about a tenth of a millimetre of wear.
• The planetary gearset, which is what low pressure eventually destroys. This is the point at which a repair becomes a replacement.

A distinct symptom worth naming, because it is mechanical rather than hydraulic: a sharp kick or impact on the shift, which is the clutch drum clearance having opened up from its factory figure. It is not the same complaint as the soft shudder a tired lock-up clutch produces, and the two lead different places.