Wheel Bearings

How a wheel bearing works

A wheel bearing is a set of rollers or balls riding on a hardened race, letting the hub spin with little friction while carrying the vehicle's weight and cornering loads. Tapered roller bearings, common on solid axles, are installed in pairs with an inner and an outer bearing on each hub, and are adjusted with a spindle nut for proper preload.

Signs of wear

• A hum or growl that changes with vehicle speed, often louder when turning one way.
• Looseness or clunking when you rock a lifted wheel by hand.
• Grease leaking onto the brake rotor or backing plate from a failed seal.
• Heat at the hub after a drive, which suggests over-tight or failing bearings.

A bad bearing is a safety risk. A seized or collapsed bearing can lock or detach a wheel, so address symptoms right away.

Choosing the right kit

Kits are specific to an axle model, front or rear position, and sometimes to the application year. A kit listed for a Dana 44 front axle may not fit a Dana 44 rear, and the same name can cover different bearing sizes on different vehicles. Check what the kit includes: it may list inner and outer bearings, races, a seal and sometimes the hardware, and it often covers one side only, so you may need two. Where a brand notes a bearing maker, that detail appears in the listing description. Confirm fitment for your exact vehicle, and measure or identify the axle first if you have swapped axles.

Installation and setup

Clean the hub and spindle thoroughly, press races in squarely with the right driver, and pack the bearings fully with grease suited to wheel bearings. Use a new seal every time. Preload and spindle nut torque matter a great deal, as both too loose and too tight shorten bearing life, so follow the manufacturer's service procedure and use a torque wrench. After installation, check for play and rotation before driving, and recheck after a short drive.

Brakes are part of the same job. Inspect the rotor, pads, caliper and hardware while the hub is off. If you are not comfortable working on wheel ends, have a qualified shop handle it.

Careful work at the wheel end pays off. Keep the work area clean, since a small amount of grit in the grease can destroy a new bearing quickly. Pack bearings by forcing grease through the rollers from the large end, not just by smearing it on the outside, and use a grease rated for wheel bearings and the heat from disc brakes. Check the spindle surface for scoring or a spun inner race, and the hub bore for wear, because a damaged mating surface will ruin a new bearing. Replace the dust cap, cotter pin or locking hardware as specified. If your axle has locking hubs, service them while you are there. After installation, spin the wheel and listen for roughness, then check again for heat after a short test drive. Regular inspection after deep water crossings can prevent a failure.