Subaru 4EAT / 5EAT

Subaru's conventional automatics — the four-speed 4EAT and five-speed 5EAT — in the Legacy, Outback and SVX.

They are longitudinal, because Subaru's flat engine and symmetrical drivetrain require it, and that alone means a procedure or a part from any transverse automatic does not describe one.

The characteristic Subaru fault is not in the gearbox at all: it is the transfer clutch. Subaru's all-wheel drive is managed by a clutch pack at the back of the transmission, and when it binds the car judders in tight turns at low speed — a car park, a three-point turn — which feels exactly like a transmission fault and is not. The fuse trick that puts the car into front-wheel drive is the standard diagnostic, and it is what separates the two.

Mismatched tyre sizes cause the same symptom and destroy the clutch pack. On a Subaru the circumference of all four tyres matters mechanically, not merely for wear — a single replaced tyre on a car with three worn ones is a real fault mechanism.

Beyond that its faults are the valve body and the solenoids, presenting as harsh engagement or a limp mode.

4EAT is a four-speed and 5EAT a five. They are the same architecture with a ratio added, which is why they share a page — and why a torque-converter or valve-body part number does not.