Front Wheel Bearing Service

Front wheel bearings designed for Front Wheel Drive (FWD) vehicles are subjected to greater loads than bearings equipped on Rear Wheel Drive (RWD) vehicles. As a result, these bearings may need to 
be replaced more often, compared to vehicles with conventional drivetrains—depending on road conditions and how the vehicle is driven. It’s important to note that FWD front wheel bearings are sealed bearings (cannot be lubricated), while most RWD front wheel bearings require lubrication.

Front wheel bearing service is pretty straightforward. Let’s review wheel bearing basics (operation and diagnosis) and wheel bearing replacement procedures.

FRONT WHEEL BEARING BASICS

On FWD vehicles, the front wheel bearing is integral with the hub and the assembly is a sealed one-piece unit. This assembly is designed to last the life of the vehicle and requires no periodic maintenance. It is either bolted to the spindle or pressed into it.

The hub and bearing assembly is mounted to the center of the steering knuckle. On minivan models, 
it is retained by four mounting bolts. These bolts are accessible from the inboard side of the steering knuckle. On LH models, it is retained by three mounting bolts. But on the PT Cruiser, the bearing/hub assembly is pressed into the knuckle.

The hub and bearing assembly has internal bearings that allow the hub to rotate with the driveshaft and the tire and wheel. The bearing is loaded primarily by the driveshaft. On RWD cars, the bearing only supports the wheel and tire.

DIAGNOSIS AND TESTING

As mentioned, the hub and bearing assembly is designed for the life of the vehicle. No maintenance, such as lubrication, is required. Although these bearings are quite reliable, failures, as with any mechanical component, do occur.

With wheel bearings, the problem is usually first noticed when making a turn. Your customer might report a noise that sounds like a whine from the front end, or a growl or grinding sound. A road test is one way to verify the problem. Find a smooth level road surface and bring the vehicle up to a constant speed. At this speed, swerve the vehicle back and forth from right to left. This will load and unload the bearings, changing the noise level.

When the vehicle is turned to the right, the left wheel bearing will make noise if it is bad. Conversely, if the vehicle is turned to the left, the right wheel bearing will make noise if it is bad.

A bad wheel bearing can also be verified by the inspection method. Raise the vehicle and remove the wheel, disc brake caliper and brake rotor on the side with the suspected bad wheel bearing. Rotate the hub. Any roughness or resistance to rotation that is felt indicates either intrusion of dirt or a bad bearing (the dirt will eventually damage the bearing). If either of these conditions are found, replace the bearing and hub assembly.

Also inspect the bearing for damaged seals and grease loss. Moderate grease weepage is considered normal, but the presence of a lot of grease around the exterior of the bearing is bad. This condition requires replacement. The same is true if the seal is damaged or missing.

FRONT WHEEL BEARING REPLACEMENT

On FWD vehicles, the wheel bearing and hub assembly is either bolted to the steering knuckle, or pressed into the knuckle. Let’s review the pressed installation first as that procedure is much more involved than the other.

Raise and support the vehicle and remove the steering knuckle in the following manner: (1) remove the wheel and tire assembly; (2) remove the cotter pin, lock nut and spring washer from the hub nut, then remove the hub nut (an assistant will be needed to apply the brakes to keep the hub from rotating); (3) remove the disc brake caliper and rotor; (4) remove the wheel speed sensor; (5) separate the outer tie rod end from the steering knuckle; (6) separate the ball joint from the steering knuckle; (7) detach the strut from the steering knuckle and (8) pull the steering knuckle off the halfshaft stub of the outer CV joint.

With the steering knuckle removed, the wheel bearing and hub can be removed and replaced. Using special tool C-4150A, press out the three wheel studs across from one another. Rotate the hub to align each wheel mounting stud with the notch in the bearing retainer plate before removal (Figure 1). The reason the three studs are removed is to allow the bearing splitter, special tool 1130, to be installed behind the flange as shown in Figure 2. Install the bearing splitter and hand tighten the nuts to hold the splitter in place on the steering knuckle.

Place the steering knuckle face down in an arbor press with the bearing splitter supported by two 
steel bars. Position the remover/installer, special tool 6644-2, on the small end of the hub. Using the arbor press, remove the hub from the wheel bearing. The bearing race will usually come out of the wheel bearing with the hub as it is pressed out of the bearing. Remove the bearing splitter, then remove the three bolts that mount the bearing retaining plate to the steering knuckle. Remove the retaining plate. Place the steering knuckle back in the arbor press face down. Using special tool MB-990799, press the wheel bearing out of the steering knuckle. Re-install the bearing splitter on the hub and remove the bearing race if it still pressed into the hub.

To install a new wheel bearing and hub, be sure the bore of the steering knuckle is clean, with no signs of grease or dirt. Install the new bearing in the following manner: (1) place the steering knuckle in an arbor press supported by special tool C-4698-2; (2) place the new bearing into the bore of the steering knuckle squarely. Use special tool, 5052, to install it in the steering knuckle (be sure the bearing is fully bottomed in the bore of the knuckle); (3) remove the knuckle from the press; (4) install the bearing retaining plate on the steering knuckle; (5) install the removed wheel studs back into the hub flange; (6) place the steering knuckle (with the new bearing) back in the arbor press with special tool, MB-990799, supporting the inner race of the bearing; (7) place the hub in the wheel bearing squarely and press it into the bearing (be sure it is fully bottomed in the wheel bearing); (8) after the knuckle is removed from the press, verify that the hub rotates smoothly.

To complete the replacement procedure, re-install the steering knuckle. This is done in the opposite sequence of the removal steps detailed previously.

As you will see, replacing a front wheel bearing and hub assembly that is bolted to the steering knuckle is relatively simple. It is done in the following manner (this is the procedure specific to minivans): (1) raise and support the vehicle and remove the tire and wheel assembly; (2) remove the cotter pin, lock nut and spring washer from the hub nut, then remove the hub nut (an assistant will be needed to apply the brakes to keep the hub from rotating); (3) remove the disc brake caliper and rotor; (4) push in on the 
end of the driveshaft stub shaft, pushing its splines out of the hub splines; (5) remove the four hub and bearing mounting bolts (Figure 3); (6) remove the hub and bearing assembly from the knuckle; Note: on LH models, the hub and bearing assembly is slid off the splines of the stub shaft after the mounting 
bolts have been removed; this differs from the minivan in which the stub shaft is separated from 
the hub and bearing assembly before the mounting bolts are removed.

When installing the new hub and bearing assembly, be careful not to damage the bearing seal with stub shaft on the outer CV joint. Also, be sure that the mounting surfaces in the knuckle (Figure 4) are clean and free of nicks before installing the hub and bearing assembly. Equally tighten the four mounting bolts in a criss-cross pattern until the hub and bearing assembly is squarely seated against the front of the steering knuckle. The other components that were removed are re-installed in the opposite sequence of the removal steps detailed previously.