Toyota U661E

Toyota's transverse six-speed for the larger front-drive cars — in the Lexus RX and NX.

It is the U660E's hybrid-era relative and shares its architecture; the catalogue holds the U660E separately because the applications and the fluid specification differ.

Its recurring complaint is a shudder at light throttle around 50–80 km/h, which is the torque converter's lock-up clutch rather than the transmission slipping — the same symptom, and the same first remedy, as on every lock-up automatic in this catalogue. On this one it tracks fluid condition closely enough that a service is a diagnostic step.

Where genuine faults appear it is the valve body and its solenoids, presenting electrically: a gear refused, a limp mode, a code naming a solenoid. Nothing slips first.

Toyota's WS fluid is required, and an RX at 150,000 km on its original fill is the commonest version of the shudder above.