Imbalance, a worn centre bearing, incorrect phasing or worn joints - and each has a distinguishable signature.

A vibration that tracks road speed regardless of gear or throttle is rotational, which points at balance, a dent or a lost balance weight.

One that appears only under acceleration and clears when coasting points at joint angles under load, worn universal joints, or tired engine and gearbox mounts letting the driveline move.

A vibration accompanied by a clunk on take-up usually means a worn centre bearing or excessive backlash somewhere in the driveline.

Mud, underseal overspray and even a heavy coat of paint are enough to unbalance a shaft, and cleaning it is free.

Check the simple causes first - wheel balance, mud on a wheel, and the centre bearing - before removing anything.

It supports a multi-piece propshaft between sections so each length runs stably, and it fails when its rubber mounting perishes.

A single long shaft would whirl at speed, so long propshafts are split and supported at the join.

The bearing itself is carried in a rubber isolator that allows small movements and damps vibration.

As the rubber perishes, cracks or separates, the shaft is no longer held in line - which gives vibration at speed and a clunk as drive is taken up.

Look for cracked or displaced rubber, and for a bearing that feels rough or has detectable play when the shaft is moved by hand.

It is usually available separately from the shaft, though pressing it on and off requires the shaft to be removed and often rebalanced afterwards.

It is the rotational alignment of the yokes at each end of a shaft, arranged so that one universal joint's speed fluctuation cancels the other's.

A single universal joint working at an angle speeds up and slows down twice per revolution.

Two joints with their yokes correctly aligned and at equal angles cancel that fluctuation, so the output turns smoothly.

Assemble the shaft with the yokes out of alignment and the two fluctuations add instead of cancelling, producing a vibration that balancing cannot fix.

On a sliding-spline shaft it is easy to pull the halves apart and reassemble them one spline out, which is exactly this error.

Mark both halves clearly before dismantling. It takes seconds, and it decides whether the shaft works or vibrates inexplicably.

Because the distance between the gearbox and the axle changes as the suspension moves, so the shaft must be able to extend and retract.

An axle on leaf springs or links swings through an arc, and that arc changes its distance from the gearbox.

A sliding spline at one end, or a plunging joint on a driveshaft, absorbs that change continuously while transmitting torque.

A seized slip joint cannot absorb it, so the length change is forced into the gearbox output bearing and the axle pinion bearing instead.

That produces a shudder on take-up and, over time, expensive bearing damage at both ends.

Many slip joints have a grease nipple and belong on the lubrication schedule - a point that is frequently missed because the shaft is out of sight.

Yes - joints, centre bearings and slip yokes are all replaceable, and specialist shops rebuild and rebalance shafts routinely.

Universal joints are pressed out and replaced, which is standard practice and well within a competent workshop's ability.

A bent tube can sometimes be replaced within the existing yokes, which is common on commercial vehicles.

The essential step is rebalancing afterwards on a dynamic balancer, because any dismantling disturbs the original balance.

A shaft repaired without rebalancing will very often vibrate, and the vibration gets blamed on the new joints.

Exchange shafts are also available for common platforms and are frequently the faster route where downtime matters more than the price difference.

Support it at both ends, mark the flanges, and never let it hang on one joint - and keep the bearing caps on any joint being reused.

A propshaft is heavy and letting it drop puts the whole weight through one universal joint, which can damage it.

Mark the flange positions relative to the gearbox and axle before undoing them, so the shaft goes back in the same rotational position.

On a joint held by loose bearing caps, secure them with a clip or tape - if a cap falls off, the needle rollers go with it.

Flange bolts are often single-use and are frequently very tight; a proper torque figure applies on reassembly.

Check the flange faces and the centring spigot for corrosion and clean them, because debris there introduces run-out directly.

Greasing where nipples exist, and inspection for play, boot condition, balance weights and centre bearing rubber.

Greasable universal joints and slip yokes are common on commercial vehicles and belong on the lubrication chart with a defined interval.

Check joints for play by gripping the shaft either side of the joint and twisting; any detectable movement is wear.

Look for missing balance weights, which leave a clean patch where they were welded, and for dents in the tube.

Inspect the centre bearing rubber for cracks and separation, and check the bearing itself turns smoothly.

Clean off accumulated mud and underseal at service. It is free, it takes a minute, and it prevents a vibration complaint.