Bearing Down: Repacking Wheel Bearings
April 18, 2013
Filed under Top Stories, Trailer How To
Greasing wheel bearings isn’t the most enjoyable way to spend your free time. However, this messy maintenance saves you from bigger bills later.
Over time, grease breaks down. Heat produced by brakes speeds up the process. Since the trailer’s weight rides on the wheel bearings, keeping them well lubricated is critical for safe RVing.
Murphy’s dictate: If you buy replacement parts before tearing into the axle, the existing bearings will be fine. If not…. Regardless, grease seals should always be replaced. These are Lippert Components’ 3,500-pound replacement parts. The dust cap with rubber plug is for a Super Lube axle (cotter pins and Super Lube grease fittings not shown).
Bearings normally whine before they grind and ultimately fail. Unnatural sounds that vary depending on speed often indicate that the bearings need attention. It’s the proverbial squeaky wheel syndrome.
Trailer owners who do their own routine maintenance know that bearing service can be done in less time than it takes to make an appointment, drive to an RV shop and either wait for the trailer or make a return trip.
The job doesn’t require any special skills or tools. (However, bearing-service kits that include seal-pullers and drifts in varying sizes are available for serious home mechanics.) To ensure we weren’t missing any subtleties, Conejo Vacation Trailer owner Mike Niedrich demonstrated how to repack trailer bearings based on nearly 30 years’ experience.
Niedrich’s pro tips:
- Never reuse cotter pins. One of the least-expensive parts of the system is probably the most important.
- Any high-temperature wheel bearing grease will work.
- All grease isn’t always compatible among brands. Thoroughly clean all old grease from bearings, races and hub cavities using a solvent such as brake cleaner.
- In general, trailer wheel bearings should be serviced annually or every 10,000 miles, whichever occurs first. Grease also breaks down on stored trailers, allowing corrosion to form.
- Visually inspect the bearing and race surfaces. If nicks or discolorations are visible, replace all inner and outer bearings and races on both sides of the axle.
- Spindle nut torquing: Once the hub, bearings and thrust washer are in place, snug up the castellated spindle nut while spinning the drum. This seats the bearing. Then back off the nut a turn, retighten it (to about 50 ft-lb if you have a torque wrench) while spinning the drum, then back the nut off 1/4 turn. Fine-tune the nut if necessary to align its closest recesses with the cotter pin hole, or lock the nut in position with the existing tanged washer or cage-style retainer.
- Some shops squirt grease into the dust cap prior to reinstallation. Niedrich used to do this until he noticed that the grease remained in the cap until the next bearing service.
Our focus is on repacking instead of replacing (which requires using punches and drifts to extricate and reinstall the bearing races). Also, affordable bearing-packing tools are available for people who want less mess.
Major steps are shown here, both for a conventional axle and for a Lippert Super Lube axle. Remember, regularly scheduled packing means happier RVing.
Follow the guide below to see how to repack your bearings!
With the axle raised and secured and the wheel removed, carefully pull the dust cap. Repair shops use a special tool, but the cap can also be gently pried off using a chisel or large flat-blade screwdriver.
Cutting off the cotter pin will force you to use a new one for reassembly. (Some axles use lock washers or “cage” retainers to keep the spindle nut in place.)
Next, the castellated spindle nut can be unscrewed.
The thrust washer and outer bearing normally fall out of the hub when the brake drum is lifted off.
Special J-shaped tools are available that gently remove grease seals. Alternately, do-it-yourselfers normally pry out the seals using flat-blade screwdrivers. The inner bearing can then be lifted out. Old grease should be cleaned off bearings, races and hub surfaces with solvent.
Hand packing involves putting a dollop of grease in one palm. Grease is scooped into the bearing all the way around until all gaps between the rollers and cage are completely filled with fresh grease. Wearing a pair of rubber gloves for this step helps reduce the messy factor.
A cleaner method is to use a packing tool. This vat-type system uses a plunger to force grease through the bearing while it’s immersed in the grease tub.
Here’s a tool-packed bearing.
Adding another layer of grease around the rollers post-packing is recommended.
Another coat of grease is laid down on the bearing race surfaces in the hub and on the bearing’s faces.
A new grease seal is installed. A flat piece of steel and a hammer are used to evenly tap in the seal until it’s fully seated.
With the drum back on the axle, the newly greased outer bearing is slid into place. It’s best to coat its face with more grease prior to reinstalling the thrust washer and spindle nut. The nut is snugged to seat the bearing in the race, then backed off, retightened, then backed off slightly. The drum should turn freely, and the nut’s body should be inboard of the cotter-pin hole.
Brake adjustment is its own story, but it should happen in conjunction with bearing-packing. (Lippert Component’s recommended brake-adjustment interval is every 3,000 miles.)
Some axles are bored through the spindle area. Lippert calls these Super Lube. A grease fitting on the axle’s end is accessible by removing the rubber plug in the special dust cap.
On Super Lube axles, grease passes through the bore and emerges from a hole near the seal. Five to 10 slow pumps of the grease gun is recommended — too much grease can flow past the seal and onto the brakes. Even with this axle type, disassembly and packing annually or
at 10,000 miles, whichever occurs first, is recommended.