The propshaft is a generally trouble-free component, at least until a high mileage has been covered.
The wear normally takes place in the universal joints and renewal is a simple enough job. There may also be imbalance or damaged splines.
The gearbox and rear axle form part of the drive train and it is easy to mistake faults in these for faults in the shaft itself.
A test drive is a good way to start your inspection. Listen as you select first gear. If there is an audible click, return the lever to neutral and then select reverse.
Another click puts the universal joints high on the suspect list. Note that wear in the crown wheel and pinion can give a similar noise while the vehicle is stationary.
NUT AND BOLTS
The basic components of the universal joint are the cross-shaped piece of steel called (heaven knows why) the spider.
On this the roller bearings attach to the yoke at one end and the shaft itself at the other, thus allowing up and down and sideways movement.
Insert a screwdriver between the shaft and spider and prise it to and fro. Pray there is no movement because if there is, the joint must be renewed.
If there is a clonk on the overrun, this means universal joint wear is quite severe. Humming noises and shaking from beneath the car’s mid-section may indicate that the shaft requires balancing.
If the imbalance is minor, you can fit worm-drive clamps on the shaft. You can then move the tightening screw to different positions and test-drive until balance is restored and the humming ceases.
ELECTRONIC BALANCING
When this does not work, you may have to get the shaft professionally treated and have weights welded on and electronic balancing carried out. Removing the shaft is simple enough and bit of DIY here will save you cash. Be certain to file a mark across the yoke and cross flanges before removal, thus enabling the return of the shaft in its original position.
Start shaft removal at the rear. Undo the flange nuts, pull the shaft down at the back and draw the slip yoke from the gearbox end. On two-piece shafts you will need to undo the bolts that secure the centre bearing to the floor pan. With the shaft removed, you will need a sturdy vice, hammer and circlip pliers
STRIPPING THE UNIVERSAL JOINT
Support the shaft flange in the vice jaws then hit it just behind the joint with a soft-faced hammer. In effect you are supporting one cross of the spider while knocking the shaft downwards to push the top bearing out.
When there is enough of the bearing cup exposed, turn the shaft over and grip the cup in the jaws of the vice and knock the shaft upwards. Repeat the operation on the opposite cup. The flange can then be twisted and removed from the shaft body.
To remove the remainder of the joint from the flange, open the vice jaws a bit wider than the cap and with the flange on top of the vice the cap may be drifted into the shaft, thus driving out the bottom cap through the vice jaws.
Grip the cup in the vice, knock the flange upwards and remove the spider. Drift out the remaining bearing cap.
Next job is the rebuild.