Axles — description and check


1. The rear axle assembly is a hypoid (the centerline of the pinion gear is below the centerline of the ring gear), semi-floating type. When the vehicle goes around a corner, the differential allows the outer rear wheel to turn at a higher speed than the inner tire. The axle-shafts are splined to the differential side gears, so when the vehicle goes around a corner, the inner wheel, which turns more slowly than the outer wheel, turns its side gear more slowly than the outer wheel turns its side gear. The differential pinion gears roll around the slower side gear, driving the outer side gear (and tire) more quickly.

2. An optional locking limited-slip rear axle is also available. This differential allows for normal operation until one wheel loses traction. A limited-slip unit is similar in design to a conventional differential, except for the addition of a pair of multi-disc clutch packs which slow the rotation of the differential case when one wheel is on a firm surface and the other on a slippery one. The difference in wheel rotational speed produced by this condition applies additional force to the pinion gears and through the cone, which is splined to the axle shafts, equalizes the rotation speed of the axle shaft driving the wheel with traction.

3. On 4WD models, a fully independent front axle assembly is used. This consists of a differential and a pair of drive axles. Each drive axle has an inner and outer constant velocity (CV) joint. Because the differential — like the transfer case — is offset to the left, the distance between the differential and the right front wheel is greater than the distance from the differential to the left wheel. In order to use two equal-length drive axles, an extension axle shaft is employed on the right side to make up the difference.


4. Often, a suspected axle problem lies elsewhere. Do a thorough check of other possible causes before assuming the axle is the problem.

5. The following noises are those commonly associated with axle diagnosis procedures:

a) Road noise is often mistaken for mechanical faults. Driving the vehicle on different surfaces will show whether or not the road surface is the cause of the noise. Road noise will remain the same if the vehicle is under power or coasting.

b) Tire noise is sometimes mistaken for mechanical problems. Tires which are worn or low on pressure are particularly susceptible to emitting vibrations and noises. Tire noise will remain about the same during varying driving situations, where axle noise will change during coasting, acceleration, etc.

c) Engine and transmission noise can be deceiving because it will travel along the driveline. To isolate engine and transmission noises, make a note of the engine speed at which the noise is most pronounced. Stop the vehicle, place the transmission in Neutral and run the engine to the same speed. If the noise is the same, the axle is not at fault.

6. Because of the special tools needed, overhauling the differential isn’t cost effective for a do-it-yourselfer. The procedures included in this Chapter describe axle shaft removal and installation, axle shaft oil seal replacement, axle shaft bearing replacement and removal of the entire unit for repair or replacement. Any further work should be left to a qualified repair shop.

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