Often the front wheel hub bearing assembly for driven and nondriven wheels is actually two tapered bearings facing each other.
Exploded view of a typical front wheel bearing assembly for a FWD vehicle. Courtesy of DaimlerChrysler Corporation
Each of the bearings rides in its own race. Some front wheel bearings are sealed units and are lubricated for life. They are replaced and serviced as an assembly. Others are serviceable and require periodic lubrication and adjustment.
Except when making slight adjustments to the bearings, the bearing assembly must be removed for all service work.
- This is done with the vehicle on lifts and the wheel assembly removed.
- In the center of the hub there is a dust (grease) cap.
- Using slip-joint pliers or a special dust cap removal tool, wiggle the cap out of its recess in the hub.
A special tool for removing a dust cap. If one is not available use slip-joint pliers.
- Now remove the cotter pin and nut lock from the end of the spindle.
- Loosen the spindle nut while supporting the brake assembly and hub.
- On many vehicles you will need to remove the brake caliper to remove the brake disc and hub.
- Once the hub is free to come off the spindle, remove the spindle nut and the washer behind the nut.
- Move the hub slightly forward, then push it back. This should free the outer bearing so you can remove it.
- Now remove the hub assembly. A grease seal located on the back of the hub normally keeps the inner bearing from falling out when the hub is removed.
- To remove the bearing assembly, the grease must be removed first. In most cases, all you need to do to remove the seal is pry and pop it out of the hub.
- The inner bearing should then fall out.
- Keep the outer bearing and inner bearing separated if you plan on reusing them.
- Wipe the bearings and races or use brake parts cleaner to clean them.
- While doing this, pay close attention to the condition and movement of the bearings. The bearings need to rotate smoothly.
- Also visually inspect the bearings and races after they have been cleaned. any noticeable damage means they should be replaced.
- Also inspect the spindle. If it is damaged or excessively worn, the steering knuckle assembly should be replaced.
- Whenever a bearing is replaced, its race must also be replaced.
- Races are pressed in and out of the hub. Typically the old race can be driven out with a large drift and a hammer. Once the race has been removed, wipe all grease from the inside of the hub.
- The new race should be installed with the proper driver.
- During assembly, the bearings and hub assembly must be thoroughly and carefully lubricated.
- Care must be taken not to get grease on the brake disc or on any part that will directly contact the disc.
- Always use the recommended grease on this assembly. The grease must be able to withstand much heat and friction. If the wrong grease is used, it may not offer the correct protection or it may liquefy from the heat and leak out of the seals.
- The bearings should be packed with grease. It is important that the grease is forced into and around all of the rollers in the bearing. Merely coating the outside of the bearing with grease will not do the job.
- A bearing packer does the best job at packing in the grease. If one is not available, force grease into the bearing with your hand. Install the greased inner bearing into the hub.
- Install a new grease seal into the hub.
- To avoid damaging the seal, use the correct size driver to press the seal into the hub.
- Lubricate the spindle, then slip the hub over the spindle. Install the outer bearing, washer, and lock nut.
- The lock nut should be adjusted to the exact specifications given in the service manual.
- Often it is tightened until the hub cannot rotate, then it is loosened about one-half turn before it is set to the specified freeplay. The initial tightening seats the bearings into their races.
- Once the lock nut is tightened, install the nut lock and use a new cotter pin to retain the lock.
- The adjustment of the bearings can be checked with a dial indicator.
Wheel bearing adjustments can be checked with a dial indicator. Reprinted with permission.
- Mount the base of the indicator as close as possible to the center of the hub.
- Locate the tip of the indicator's plunger on the tip of the spindle.
- Set the indicator to zero.
- Firmly grasp the brake disc and move it in and out.
- The total movement shown on the indicator is the amount of freeplay at the bearing.
- Compare your reading to the specifications and make adjustments as necessary.
Throughout this entire process, your hands will have grease on them. Be very careful not to touch the brake assembly with your greasy hands. Clean them before handling the brake parts or use a clean rag to hold the brake assembly.
- The front bearing arrangement often found on FWD and 4WD vehicles is often nonserviceable.
- These bearings are pressed in and out of the hub to be replaced. To do this, the axle or half shaft is removed, as is the steering knuckle and hub assembly.
- The bearings may be sealed and require no additional lubrication or they may need to be packed with grease when they are reassembled. In most cases, the bearings are not adjusted.
- A heavily torqued axle nut is used to hold the assembly in place on the axle.
- This nut is typically replaced after it has been removed and is staked in place after it is tightened.