ZF 5HP

ZF's longitudinal five-speed family — in the BMW Z3 and much of BMW's range, the Range Rover L322's V8, and across Audi, Jaguar, VW and Porsche.

The number after the 5HP is torque capacity, not a generation: the 5HP18 and 5HP19 are the small ones, the 5HP24 and 5HP30 the large. Two cars of the same make and year carry different members, chosen by the engine, and their parts do not interchange.

Its defining failure is the valve body and the sealing rings, and the symptom sequence is the useful part: a delayed or harsh engagement into drive when cold, then a flare on one change, then slipping. The early stage does not feel like the start of a failure, and by the time it does the clutch packs are usually gone.

These were the first widely-sold "lifetime fill" automatics, which is most of why so many died early. They are not sealed for life, the fluid is a specific ZF specification, and a unit at 200,000 km on its original fill is the commonest version of every complaint above.

The 6HP that replaced it has a mechatronic unit and quite different failures; a procedure written for one does not describe the other.