I called my older brother and he said you should check the seal (the piece between the axle and the hub on the back of the wheel). If it is old, cracked or brittle, the grease might leak out and then your axle/hub will overheat and you might see it going by in front of you as you are going down the road. The problem is that if you pull the tire off, you will probably ruin the seal anyway. There are some numbers on the seal that might help you find the right size. There is a spring at the inside center of the seal that needs to be in the proper place.
You may not need to pull the hub if there is a grease nipple into the hub like my quality Harbor Freight trailer had.
I am open to comments on how to tell without pulling off the seal but you should at least visibly check.
- You take the wheel off
- You pull the dust cap off the center of the hub
- You pull the cotter pin (don't lose it)
- You unscrew the slotted nut
- Pull out the hub and a washer and a bearing will come out.
- You can put the slotted nut back on and use it to pull the seal and bearing out the back but it will damage the seal. I used a bicycle handle because it wasn't as rigid and didn't hurt the seal as much as the PVC pipe I used. Something rubber will probably suffice (maybe a screwdriver handle?)
- Get a lot of paper towels because the grease is nasty.
- Use gas to wash off the parts (or some degreasing agent if you don't like the thought of handling gas).
- Decide if you need a new seal.
- I used blue marine grease because it was for a boat trailer.
- Put the grease in the palm of your hand and smash the back of the bearing in it. You can return the excess to the palm of your hand.
- Repeat above until there are no gaps in the bottom of the bearing.
- Push the front of the bearings into the blob of grease in your palms making sure you cover the gap in the front of the bearing.
- Put some extra grease inside the seal and inside the hub (the hub does not need to be completely full)
- Put the inside bearing in (my bearings were both the same size but the larger bearing usually goes on the inside) with the narrow end in first and then tap the seal in using a rubber mallet or board on top of the seal so the seal is not damaged.
- Put the hub back on and put some more grease where the outside bearing will go.
- Put the outside bearing in with the narrow end in first (it will be like this > < ).
- Put the washer on with the scored/scarred side in first.
- Maybe put in a little more grease outside the bearing
- Put the slotted nut on and and finger tighten
- IMPORTANT: put the cotter pin back in.
- Put the dust cap (or bearing buddy) back on and then put the wheel on.
Here is a Youtube video that I found helpful (I liked to hear him call it the carter pin too):
https://www.youtube.com/watch?v=akh0WhkudrM
