Reconditioned Citroën C4 1.6 HDi Gearbox

Five speeds or six, manual or BMP6: three different gearboxes for a single 1.6 HDi

The 1.6 HDi fitted to the C4 covers several engine codes — 9HX, 9HZ, 9HY, 9HP, 9HR, 8HX, 8HZ — and depending on the year (2004 to 2018) and the variant, it may have been paired with a 5-speed manual, a 6-speed manual, or the BMP6 automated gearbox. These three families are not interchangeable: a reference such as 20ET07 or 20DP72 is tied to a specific engine code, not simply to the engine capacity. Mixing up a 5-speed and a 6-speed, or assuming a BMP6 can replace a manual, will result in an unusable order.

Engine code and number of ratios: the two filters you must apply

The 5-speed gearboxes are fitted to the lower-powered versions of the 1.6 HDi, most commonly associated with engine codes 9HX and 8HX. The 6-speed units appear on the more recent or higher-powered variants (9HY, 9HR). The BMP6, an automated gearbox with an electrohydraulic actuator, is supplied without the actuator: the actuator is not included with the mechanical gearbox.

Typical symptoms by gearbox family

On the 5- and 6-speed manuals, the most common failures affect the 3rd and 4th gear synchronisers, with stiff gear changes when cold that progressively worsen into a refusal to engage. The BMP6 presents a different profile: jerky changes and refusal to shift are often caused by the actuator or the mechatronic unit rather than the mechanical gearbox itself — pinpointing the exact source of the fault before placing any order is essential.