Toyota U660E

Toyota's first six-speed automatic for front-wheel drive, introduced in 2006 and built by Aisin. Its achievement was packaging rather than ratios: it went into the space a four-speed had occupied, using a Lepelletier gearset — a simple planetary set driving a Ravigneaux one — to get six ratios out of far fewer parts than a conventional layout would need. It is rated to 400 Nm and has been behind Toyota's 3.5 V6 in one car or another for nearly twenty years.

The single thing to establish before reading any further is which of the two you have. Toyota built this six-speed in two duty classes and they are not interchangeable:

• The U660E — this unit — is the heavy-duty one, and it sits behind the V6.
• The U760E is the light-duty one, introduced two years later for the four-cylinder cars.

So a Camry is not a Camry for these purposes: the 3.5 has this gearbox and the 2.5 has its sibling. They share a design and a great many symptoms, and they do not share part numbers.

One application is worth knowing about because it looks like a mistake and is not. The Lotus Evora is a rear-wheel-drive mid-engined sports car running this front-wheel-drive transaxle — the engine is mounted transversely behind the driver, so the same unit simply faces the other way. A reader who finds a Toyota Camry gearbox in a Lotus has found the truth.

Its signature failure is small, specific and worth naming first: the main housing bearing, which is held by a circlip the trade considers too weak for the job. That is the commonest fault on the unit, and it matters beyond itself — a bearing that has begun to move puts vibration through everything downstream, and what an overhaul then finds is damage to the crown gear, the sun gear, the planetaries and the differential. The cheap part is upstream of the expensive ones.

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

• The C1–C2 direct clutch drum, whose cover burns — and unusually early, sometimes between 70,000 and 100,000 km.
• The B1–B3 brake pack frictions, which serve second and sixth gear and are replaced as a complete set rather than individually.
• The valve body, whose channels and plunger valves silt up. This is a consequence rather than a cause: what contaminates the fluid is usually a torque converter that has already begun shedding its lock-up lining.
• The pistons, which the trade orders on almost every overhaul of a unit that has been run hot.

One diagnostic trap is specific enough to be worth stating outright. An overheated temperature sensor is frequently mistaken for a valve body fault, because the symptoms it produces are the ones a bad valve body produces. Checking the sensor is cheap and comes first.

On fluid, the honest position: Toyota specifies ATF WS — the World Standard fluid — and sold these cars with no service interval, which owners reasonably read as never. Every source that works on them disagrees, and the reason is the sequence above: the converter sheds lining, the lining reaches the valve body, and the valve body is what everybody ends up paying for. Changing the fluid does not prevent the circlip letting go, but it does break the one chain on this list that is genuinely preventable.