Servicing the increasing number of vehicles equipped with pressed-in wheel bearings requires a little bit more finesse and tools when compared to hub units or tapered roller bearings. However, with the right tools and information, these jobs can be money-makers.
For example, the driver of a 2002 Jaguar was complaining about noise. The vehicle’s ABS light was illuminated and the speedometer was inoperative. The noise was confirmed on the test drive and was isolated with the vehicle in gear running on the lift. The bearing and knuckle design was used on Ford, Mazda and Volvo. No data was being transmitted from the wheel speed sensor to the scan tool. The engine control module uses this wheel speed sensor to drive the speedometer.
As a rule, there should be no perceptible play in the wheel bearing. On this vehicle, there was no endplay, but the bearing was very noisy.
Remove the axle nut while the brake caliper bracket is still on the vehicle. Lock the rotor into place with a punch in the fins of the rotor. On vehicles with solid rotors, remove the nut while the vehicle is on the ground with the wheel on the vehicle. Do not use an impact wrench because damage can occur to the CV joint or differential.
Remove the caliper bracket and rotor. Inspect the wheel flange for damage and any signs of distortion. A damaged flange can cause runout and ultimately a pulsation complaint.
On most late-model vehicles, active wheel speed sensors are mounted in the knuckle, see Photo 1. Active sensors have two wires and the relator wheel is part of the rear seal or the bearing. This type of sensor can be easily identified by the flat blade of its head.
Push the CV joint out of the stub axle with a forcing screw, see Photo 2; using a hammer can damage the threads on the axle. Once the CV joint is free in the splines, use a slide hammer to pull the stub axle from the knuckle. The stub axle will typically come out with the outer seal, race, bearings and carrier. If equipped, remove any C-clips in the bore.
On this vehicle, the bearing should be removed and a new bearing installed on the vehicle. Tool kits to perform this type of work are available on most tool trucks and online. They can save time by not having to remove the knuckle from the vehicle. This can save an alignment or a trip to the press. Most instructions tell users to detach the knuckle at the ball joint. In most cases, this allows the knuckle enough swing to be able to remove the CV axle. However, there is an easier way to detach the knuckle for some vehicles. On this vehicle, remove the bolt that holds the front of the control arm to allow enough clearance to pull the axle free, see Photo 3. This can eliminate damage to the ball joint boot.
Set up the tool so the rear adapter makes contact with the inside part of the bearing and on the other side should be a cup the old bearing will fall into. Lubricate the bolt of the tool before using. I recommend a few drops of 80w-90 gear lube. Do not use lightweight lubricant.
Once the bearing is removed, inspect the bore of the knuckle for damage. The bore should be free from corrosion. Check the bore for roundness using a snap bore gauge, see Photo 4. The gauge should rotate in the bore easily. Any distortion in the bore can cause a new bearing to fail prematurely.
When pressing in the new bearing, make sure the adapter does not come in contact with the seal, see Photo 5. Make sure the seal with the tone ring is facing inwards. It is recommended that an impact is not used for this part of the repair.
The stub axle and flange can be installed in a variety of ways. Using a forcing screw can do the least amount of damage if the inner race is supported, see Photo 6. Some technicians swear by freezing the flange in a freezer or with dry ice. The stub axle should not be seated fully. The final position of the stub axle should be set when the axle nut is tightened and the final pre-load is applied.
Don’t reuse the old hub nut on the axle if possible. Install a new one and torque to bearing or OEM specifications, see Photo 7. It is nearly impossible to give a general torque specification for a locking nut. There can be large differences depending on bearing type and housing.
The reason why this bearing failed is two-fold. First, there was a significant impact that caused the balls to make a mark in the outer race. When a vehicle hits a curb, pothole or other object in its path, the force is transferred to the small surface area of the bearing. The impact may cause damage to the races and the rollers/balls. This damage is called brinelling.
Brinell marks may cause the bearing to make noise immediately or it may not. But, as the marks keep rotating, it is damaging the entire bearing. If the impact is great enough, the pre-load on the bearing can change. This can lead to more damage and noise.
On this bearing, it is obvious the pre-load was destroyed by the condition to the seals, see Photo 8. On the inner seal, the balls impacted the seal. The reluctor ring on the outer seal shows signs of heat damage, see Photo 9. When the ring separated from the rubber material, the wheel speed sensor stopped working. The tone ring is magnetic and can be detected using a card that detects the permanent magnets in the seal.
For more tips on bearings, courtesy of SKF, visit http://www.skf.com/binary/30-61905/TT08_014.pdf.