Block the trailer tires on the opposite side securely so that no forward or reverse movement is possible.
Secure the trailer on jack stands of adequate capacity, front and rear.
Removing the Wheel & Hub
Undo the wheel nuts/bolts and remove the wheel.
Pry off the dust cap using a flat head screwdriver.
Straighten out the cotter pin that holds the castle nut and remove it.
Remove the castle nut.
Cup the hub opening with your hand to keep the outer bearing from falling to the ground. The race stays in the hub, while roller bearing comes out as an assembled unit.
Place the outer bearing and castle nut in a clean container.
Removing the Grease Seal & Inner Bearing
Place the hub face down so that the back of the hub is accessible.
Pry out the grease seal.
Lift out the inner bearing and place it in the container with the rest of the parts. Don't mix up the bearings if you are doing more than one wheel at a time - each bearing must mate with its original race.
The bearings wear in by a certain amount and need to be matched with their respective counterparts.
Inspection of Bearing
Thoroughly clean the bearings and other parts in a solvent or degreaser (not gasoline!) until all the old grease is removed.
Set the parts aside to dry completely or blow dry with compressed air.
Don't use the air pressure to spin the bearing, as damage could result to the bearing or to your person.
Clean the hub and spindle.
Inspect the bearing races for heat discoloration, pitting, scoring, and any unevenness.
If the races are damaged, you will need to replace the entire hub.
Inspect the bearing for damage as noted above. Any out of round rollers, cracked roller cages, and rough running will indicate that replacement is required.
Hand-packing the Bearing
Inexpensive bearing packers can be purchased from most auto parts stores that work well with the small tub of bearing grease.
Place a walnut sized gob of wheel bearing grease in one palm.
Grasp the bearing with the other hand so that the wider end is facing the grease.
Force the grease into the gap between the inner race and the outer cage so that it squeezes up through the rollers and out the top.
Press the bearing down into the grease in a rocking motion and continue until the grease oozes up.
Rotate the bearing 1/4 turn at a time, and continue until the bearing is completely filled with grease.
Re-assembly
Put some grease into the interior of the hub with your fingers. A walnut sized amount is sufficient.
Spread it around the circumference of the hub.
Place the inner packed bearing into its place in the hub.
Place a new seal on the hub and tap it into place with a hammer until it seats fully.
Always use new seals. Never try to reuse the old ones!
Be sure to wipe off any grease that finds its way onto the outer flat surface of the seal.
Replace the hub onto the axle spindle. Insert the outer bearing and reinstall the castle nut.
Pre-loading the Bearings
Tighten the castle nut by hand until it is finger tight.
Tighten another 1/4 turn with pliers or wrench.
Spin the hub several times to distribute the grease evenly in the bearings.
Back off the nut with the pliers or wrench, until loose and then retighten finger tight.
Insert a new cotter pin to lock the nut in place and bend it over the spindle.
Re-install the dust cap, tire, and wheel bolts/nuts.
