Citroen DS5 Pinion Gear

In the differential it is a whine that builds under acceleration and fades when you lift off, because load on the tooth flanks changes as the drive direction reverses. In the steering it is notchiness right at the straight-ahead position, where the rack teeth see the most use. Both usually arrive alongside an oil weep, since the same wear that makes noise also lets the seals go.

A complete rack-and-pinion replacement fitted runs R7,500 to R18,550 at a specialist. Differential pinion work costs more, because the crown wheel and pinion have to be replaced as a matched pair and then shimmed to the correct backlash and preload — that setup is the skilled part and it cannot be rushed. Pro Citroen Spares can source used racks and complete differentials, which often beats a rebuild.

A whine under load that tracks road speed rather than engine speed points at the crown wheel and pinion mesh or at dry gearbox bearings. The test that separates them costs nothing: get to speed, dip the clutch and coast. If the noise continues unchanged, it is downstream of the clutch and driven by road speed. If it changes or fades, it is engine or input-shaft related.

A specialist can replace the pinion and crown wheel as a matched set — they are lapped together at manufacture and must be replaced together. What makes it expensive is not the parts but the setup work, measuring backlash and bearing preload and shimming until both are within specification. On most Citroens, where the differential lives inside the gearbox, a used complete unit costs less than that labour.

Pro Citroen Spares sources used steering racks and complete differentials for the C3, Xsara, C3 Aircross and C5, with further drivetrain parts through our supplier network. Send the VIN and the transmission code, and tell us which noise you are chasing — steering and differential parts are entirely separate, and the descriptions people arrive with often fit both.