ZF 4HP14

ZF's small transverse four-speed — in the Peugeot 306 and 405, and the Daewoo Leganza and Nubira.

A Daewoo and a Peugeot sharing a gearbox is not obvious from either car, and it doubles the useful literature in both directions: much of what exists is written in French about the 405.

Its recurring failure is the solenoid and valve body, producing a harsh or delayed engagement, a change that arrives at the wrong road speed, or a limp mode locked in third. These are cars old enough that a limp mode reads as terminal, and on this transmission it very often is not.

The fluid is Dexron II or III and the interval is real. These predate the sealed-for-life fashion entirely, so the maintenance was specified and is simply often skipped — a unit with unknown fluid history is worth servicing before any diagnosis is attempted, because worn fluid produces every symptom above on its own.

It is not the AL4/DP0 that replaced it in the Peugeots. The two overlap by model year on some cars, share no parts, and have quite different failure modes.