A worn outer CV joint - few automotive symptoms come closer to conclusive.

The click is the worn balls skipping in damaged tracks, and it needs both steering angle and drive torque to appear.

It is loudest on full lock under acceleration, and it comes from the wheel on the outside of the turn.

Reversing on full lock usually makes it more pronounced, which is a useful confirming test in a quiet yard.

By the time it clicks the joint is beyond repair; the only decision left is joint versus complete shaft.

A clunk rather than a click, felt on take-up, is more likely the inner joint or the differential.

Because the joint is fine until the boot splits and scrap a few thousand kilometres later - the boot is what determines the joint's life.

It retains the specialised grease the joint needs and excludes water and abrasive grit.

Grit turns the grease into a lapping compound, and the wear that follows is rapid and irreversible.

A split found early allows the joint to be cleaned, repacked and re-booted at a fraction of the cost of a new shaft.

Boots split from age, ozone and heat as well as impact, so low-mileage vehicles are not exempt - and vehicles that stand are particularly prone.

Grease flung around the inside of the wheel arch is the classic sign, and it is visible from a metre away at any service.

The outer joint is fixed and works at large angles for steering; the inner joint plunges to absorb the shaft's length change as the suspension moves.

A fixed ball-type joint accommodates large angular movement but no change in length, and a driven, steered wheel can accept nothing less.

A plunging joint, usually a tripod design, slides axially while transmitting torque, absorbing the distance change between the differential and the hub.

They are not interchangeable, and each has its own boot and often its own grease specification.

The outer joint announces wear as clicking on lock; the inner announces it as vibration or shudder under acceleration in a straight line.

Some rear-drive and four-wheel-drive layouts use CV joints at both ends of a propshaft for the same reasons, with a plunging joint at one end.

Yes. CV joints use a specific molybdenum-bearing grease, and ordinary chassis grease will not do the job.

The joint runs with very high contact pressures between the balls and their tracks, which needs an extreme-pressure additive package.

Inner tripod joints often specify a different grease from outer ball joints, and the two should not be substituted.

The correct grease is supplied in the boot kit in the correct quantity, and using all of it matters - underpacking starves the joint, overpacking bursts the boot as it heats.

Never mix greases: incompatible thickeners can separate and release their oil.

If the joint is being repacked after a split boot, it must be dismantled and cleaned thoroughly first, because new grease over contaminated grease achieves nothing.

Usually the whole shaft, once labour is counted - it renews both joints and both boots for not much more than one joint fitted.

The labour to remove the shaft is the same whether one joint or the whole assembly is replaced.

A complete shaft arrives assembled, greased and booted, which removes several opportunities for error.

It also renews the joint that has not yet failed but has done identical work.

Individual joints and boot kits earn their place on heavy vehicles, on shafts that are expensive or hard to source, and where only a boot has split on an otherwise young joint.

Remanufactured exchange shafts are widely available for common platforms and are generally the fastest route back into service.

Split or stretch boots allow it, and they are a legitimate compromise - but a conventional boot fitted with the shaft out is the better repair.

A conventional boot has to pass over the joint, which means dismantling the shaft.

Split boots are supplied open and bonded or clipped together in place, and stretch boots are forced over the joint with a special cone tool.

Both avoid removing the shaft and both are quicker, which matters when the joint itself is sound.

The weakness is the joint or the seam, and a poorly bonded split boot fails again quickly.

Neither method allows the joint to be properly cleaned and repacked, so they are only appropriate where the boot has just split and no contamination has entered.

The gearbox or differential output seal, the hub nut and the wheel bearing - all accessible at that moment and awkward afterwards.

The output shaft seal is easily damaged during removal and often already weeping, and it is inexpensive.

Hub nuts are usually single-use, frequently staked, and torqued very highly - the correct new nut should be to hand before starting.

With the shaft out, the wheel bearing can be checked properly for roughness and play without the driveshaft masking it.

Inspect the circlip and the splines on both the shaft and the differential side, since a worn spline will not hold.

Check the opposite shaft's boots at the same time - they are the same age and the vehicle is already raised.