When automakers started using sealed wheel bearings back in the 1980s, many technicians thought wheel-bearing service was a thing of the past — at least for newer vehicles. True, sealed bearings don’t need any maintenance or adjustments, but that doesn’t mean they last forever. Like any moving part on a vehicle that is subject to wear and contamination, wheel bearings can and do wear out.
The first symptom of wheel bearing trouble is usually noise. A rumbling, growling, chirping or cyclic noise of any kind from the vicinity of the wheels is a good indication that the bearings need to be inspected without delay.
Wheel bearing noise is usually proportional to vehicle speed, and does not change when accelerating, coasting or decelerating (which distinguishes it from differential, transmission or U-joint noise). The noise may change when turning, or become louder or even disappear at certain speeds. But it shouldn’t be confused with the clicks and pops produced by a worn or damaged outer CV joint on a FWD car. A bad outer CV joint usually only makes noise when turning, not when driving straight ahead.
If a sealed bearing assembly is noisy or feels rough when the wheel is spun by hand, it needs to be replaced. If the bearings are the serviceable kind, they need to be removed, disassembled, cleaned and inspected. If the rollers, balls or races are worn, pitted, cracked or show any damage, replacement is required.
Note: bearings and races must always be replaced as a matched assembly. Heat discoloration indicates loss of lubrication or overtightening.
The bearing hub bore should also be inspected for damage and proper bearing fit. If the bore is damaged or does not hold the race snugly, your customer will need a new hub, rotor or drum.
Spindles on rear-wheel drive vehicles also need to be inspected for straightness, damage or cracks. Any problems here would also call for replacement.
Another problem that may occur with older, serviceable wheel bearings is incorrect adjustment. Too much play can allow steering wander (which may be mistaken for worn steering components or the need for an alignment). One way to check wheel-bearing play is to raise the wheels off the ground and rock the tires in and out while watching for any looseness. As a rule, there should be no play on most FWD cars, but up to .010 inch of play in the front bearings may be acceptable on RWD cars and trucks with adjustable bearings.
If there’s play in sealed bearings, replacement is necessary. But if the bearings are the adjustable variety, a simple adjustment might be all that’s needed.
In any event, "loose" wheel bearings should not be adjusted until the bearings have been removed and inspected for possible damage. Bearings do not loosen up under normal use. So if the bearings feel loose, they may be adjusted too loose, worn or the hub nut may have backed off (a broken cotter pin or retainer).
Wheel bearings that are not factory sealed on older vehicles require periodic maintenance. But many are neglected and never receive any maintenance whatsoever except maybe when someone is doing a brake job. Serviceable bearings should be cleaned, inspected and repacked with fresh, clean wheel bearing grease every 30,000 miles or according to the vehicle manufacturer’s recommendations.
In the case of trailer wheel bearings, even more frequent maintenance is required if the bearings have been under water. With boat trailers, annual cleaning, inspection and regreasing is highly recommended at the end of the season.
When wheel bearings are serviced, the old grease should first be removed and the bearings cleaned and inspected before being repacked with fresh grease. This will remove any contaminants from the hub that may cause problems later on, and eliminate any risk of incompatibility between the old and new grease.
Use a quality high temperature wheel bearing grease (a #2 NLGI lithium-based grease, for example) or a synthetic wheel bearing grease. Three heaping tablespoonfuls is usually enough for most car and light truck hubs. The hub should not be packed solid with grease to allow room for expansion.
When wheel bearings are installed, use new grease seals. Never reuse old seals. Used seals can leak and contaminate brake linings or cause premature bearing failure.
Adjust the bearings to specifications. Overtightening adjustable tapered roller bearings is a common error that can lead to premature failure. Tapered roller bearings on the front of RWD vehicles are never preloaded. They’re snugged up with no more than 15 to 20 ft. lbs. of torque while rotating the wheel to make sure the bearings are seated. Then the adjustment nut is loosened 1/6 to 1/4 turn, and locked in place with a new cotter pin. As a rule, end play should be about .001 to .005 inches.
On FWD cars with adjustable tapered roller rear wheel bearings, the bearing adjustment procedure is usually the same as with RWD vehicles (zero preload), but some do require a slight preload. Ford, for example, says the rear wheel bearings on older Taurus models should be lightly preloaded to 24 to 28 in. lbs. (2 ft. lbs.).