The strength of the BMW M4 Coupé is evident in every detail.
There are still many cars around with propshafts to take the drive from the front-mounted engine to the live rear axle and generally they give many years of trouble-free service.
The basic components are the piece shaped like a cross (spider) to which the roller bearings are attached, hence the name, cross and roller universal joint. Other parts are the yoke and the shaft itself.
Propshafts are tough, but with wear unwelcome noises, albeit slight at first, tend to appear. Noise may be caused by wear in the universal joints, an imbalanced shaft and a click on selection of first or reverse gear.
If there is a click both times, insert a screwdriver between the shaft and spider and prise it to and fro. If any movement is detected, the joint is due for renewal.
As universal-joint wear increases you will hear a nasty knock on the overrun. Okay, a slight noise may be ignored for a while, but worn universal joints sap engine power and there is also the danger of eventual universal joint seizure.
Propshafts are normally balanced before fitting. Imbalance can bring occasional vibration under the car and a constant humming.
Minor imbalance may be corrected by fitting worm drive clamps to the shaft and moving the tightening screw around until the imbalance is eliminated.
On a two-piece shaft a sudden imbalance may be caused by a loose carrier which holds the centre bearing.
If there is no click when selecting first or reverse, examine the extension housing bushing.
When imbalance is more serious and fitting clamps does not do the trick, the shaft must be removed and treated by a professional. He will weld on weights and then set balance electronically.
Shaft removal is easy, so if you want to save cash, do it yourself, but be certain to mark the yoke and cross flanges so the shaft can be refitted in its original position. Remove the shaft starting at the rear.
Undo the flange nuts and put a tray in place to catch escaping oil when the slip yoke is pulled from the gearbox end.
If a two-piece shaft is fitted the centre bearing will be bolted to the floor pan.
With the shaft off, the circlips must be removed either with the proper pliers, or prising them out with a screwdriver.
Never re-use old circlips.
Then support the shaft flange in a vice and use a soft-faced hammer to hit the shaft. In effect you are supporting one cross of the spider while knocking the shaft downwards to push the top bearing from the shaft.
When this is done, turn the shaft over, grip the exposed cup end in the vice and tap the shaft upwards.
Repeat the process on the opposite cup, twist the flange and remove it from the shaft body.
Open the vice jaws a little wider than the bearing cup and lay the flange on top of the vice and drift the bearing cap into the shaft, thus driving out the bottom cup through the vice jaws.
Grip the cup in the jaws knock the flange upwards and take the spider out. All that remains is to drift out the remaining bearing cap.
Next week I shall describe the rebuild. - Star Motoring