One of the most satisfying car maintenance jobs is repacking wheel bearings. It requires no special tools and it can easily be done in half a day. Tapered roller bearings are used widely on the front wheels of rear- wheel-drive vehicles and on the rear wheels of front-wheel-drive cars: in other words, on the non-driving wheels. They are the ones that can be repacked.
Wheel bearings used on the front of front-wheel-drive cars are sealed and lubricated for life. Replacing them is harder.
Similarly, the sealed bearings used on the driveshafts of rear-wheel-drive cars have to be pressed off by an engineering shop when it is time to replace them.
Usually, bearings let us know that they are in distress by making a growling, rumbling noise.
Too much play in the bearings will cause other symptoms, like steering wander, juddering action of the brakes and abnormal tyre wear.
To check for excessive play, grasp the tyre at the 12o'clock and 6o'clock positions and try to rock it.
There should be barely perceptible play on tapered roller bearings.
Also spin the tyre by hand. It should turn freely without any noise or roughness from the bearings.
The biggest threat to wheel bearings comes from dirt or water getting into them.
Dirt can get in when a hub is removed during a brake or suspension job and a bearing drops onto the floor or into a dirty parts tray. Water can get in when a seal starts leaking.
A worn or damaged grease seal will allow grease to leak out of the bearings and water and dirt to enter the bearing cavity.
Any vehicle that has been driven through hub-deep water should have its wheel bearings cleaned and repacked.
To inspect, clean, and repack tapered roller wheel bearings get the appropriate end of the car on axle stands so that the wheels you will be working on are free of the ground.
Remove the wheel and the disc-brake caliper or brake drum. Brush away dust on the brake lining. Use a screwdriver to prise the dust cover from the centre of the hub.
Straighten the split pin and extract it from the wheel-bearing nut lock. Unscrew the nut and remove the thrust washer.
The hub can now be withdrawn and the outer cone will come out by itself. On the other side is a grease seal that must be prised out with a screwdriver, after which the inner cone can be removed. The outer rings of both bearings are a press fit in the hub and can remain there unless they are damaged.
All the old grease must be removed from both bearing cones and from the bearing cavity in the hub.
Swirl the cones in paraffin while using a clean paintbrush to remove all traces of grease from between the rollers.