wheel bearing service

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Some of the toughest challenges we face as import technicians are noise complaints. And, in order to make an accurate assessment, we take the time to ask our customers questions such as: Is the noise present when the car is stationary or running? Does it change in turns or under different load considerations? Is it a growl, squeal, whine or rattle?

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Although wheel bearing noise is also one of the most difficult problems for the customer to describe, it is not unusual for it to appear so gradually that the customer may not even notice it until you mentioned it after an unreported test drive. Often the customer complaint will send you down the wrong path if you let it. We’ve heard complaints of exhaust leaks, tire balancing, “it just doesn’t sound right,” which ended up being bad wheel bearings.

When faced with a noise complaint, take the time to test drive the car with the customer, if possible.

When the vehicle is in the air and you confirm the wheel bearing problem, be sure to look at the entire job and include peripheral items in the estimate. On many models, it will be necessary to disconnect the stabilizer bar links. Do they seem to break up and get back together? It might be better to replace them. If the CV boot is torn, now is the best time to deal with it.

IMPORTANT FIRST STEPS

During your test drive, note the sound as the load changes on bends; this will give you an idea of ​​the failing bearing (noise usually increases with load). If there is no change, this indicates that there may be another problem disguising itself as a wheel bearing.

Anything that can feed a vibration into the chassis could be the problem, from worn engine mounts to misrouted air conditioning lines or, in the case of SUVs, don’t overlook the rear differential and driveshaft as the source. If in doubt, our final step in the diagnostic process is to put the vehicle on the lift and identify the problem with a stethoscope.

Pay attention to the protective bellows of the ball joints and steering ball joints as well as the threads. You also have to pay attention to the ABS sensors. If they are stuck in the case, it may be best to leave them in place and unplug them from the harness – and be careful with them when working on the bench. I like to tell techs to think about putting the work back together while they’re taking it apart.

Deletion

Always remove the wheel speed sensor first. The wheel speed sensor head can be damaged when the CV axle is pushed out of the knuckle, or a missed hammer blow can remove it.

When replacing bearing hub assemblies mounted in aluminum spindles, try heating the spindle. In most cases, the aluminum will expand enough to speed the removal of the hub assembly. But, sometimes a pneumatic hammer is the best tool. The key is to turn the hub unit in the bore to break the corrosion.

On most front wheel drive vehicles you will need to separate the ball joint or unbolt a control arm to get the drive axle out. Also, on some platforms it may be necessary to remove the stabilizer bar link.

Installation

The first step is to clean the spindle and bearing bore. If you want to prepay, coat the surfaces of the hub unit that make contact with the knuckle to make the next replacement a little easier.

Some bearings can be installed at 180 degrees – however the dust seal at the rear of the hub will prevent insertion of the wheel speed sensor if this is done.

Although it may seem easier to use an impact wrench, it is not recommended. OEM and bearing manufacturers always recommend using a torque wrench for installation. When removing, an impact wrench can strip the axle nut threads and shock the CV joints. It can also create a false sense of security when adjusting a nut or bolt, which may be under or over-tightened. This can leave a hub assembly susceptible to failure. Also, in almost all cases, use a new axle nut. Some axle nuts are designed to be used only once and cannot be adjusted.

Many hub units for FWD applications come with a new hub nut. Use it. And be sure to torque it to spec with a torque wrench – never an impact wrench.

After repairs are made, you should always confirm that the problem has been resolved by clearing all ABS codes and performing a short road test to ensure that the ABS warning light does not illuminate and that there is no rolling noise.

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