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Checking the half shafts

Half shaft on a rear wheel drive car
Half shaft on a rear wheel drive car
The half shaft is splined into the differential assembly and runs inside the axle casing.

Half shafts, otherwise known as axle shafts, are fitted in rear-wheel-drive cars only. They give relatively little trouble during normal motoring, although they are highly stressed components.

The inner end of the shaft is supported and driven by the differential , and the outer end is supported in bearings between shaft and axle housing .

These bearings have either built-in or separate oil seals . The bearings can be ball bearings , taper roller bearings (both with inner races), or straight roller bearings which use the axle shaft as the inner race.

When a half shaft fails, the rear wheels cannot be driven.

The main symptoms of a worn half shaft are a knock or clunk when accelerating or decelerating. The cause is wear and excessive play between the shaft and differential splines .

However, the same symptoms can be caused if the crown wheel and pinion gears in the differential are not meshing correctly, the drive-pinion flange splines are worn, or the drive-flange bolts are loose.

If you are not sure of the noise source, consult a garage. Special tools are needed to check wear, called between two parts such as the teeth of gears. data-term-id="1310">backlash

, in such components as the crown wheel and pinion.
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