Not enough grease and adjusting nut too tight is the typical reasons as to why bearings overheat and fail. You may have one or both..
To "pack" the bearings correctly you MUST force as much grease INTO the race, this can be done by hands and fingers or a specially made for tool for the bearings..
If you are simply wiping some grease around the race and calling it done you are under greasing the bearing. You have to take a good glob of grease and force it between the bearings until it is coming out the sides of the bearing.
Then another glob goes around the bearing and another glob on the inside of the hub..
To tighten the bearings correctly you will run the nut tight by hand, then while turning the drum tighten a little more until you feel some drag from the bearing.
Then you LOOSEN the nut 1/4 turn.
Then you tighten the nut slightly WHILE NOT TURNING THE DRUM.
You now insert the cotter pin. IF PIN HOLE DOES NOT LINE UP WITH CASTLE OPENING YOU LOOSEN NUT JUST ENOUGH TO INSERT PIN! YOU DO NOT TIGHTEN THE NUT TO ALIGN THE PIN.
The result will often be SOME slop or looseness in the bearing..
You do not "torque" the trailer axle nuts down, doing so will result bearing failure.
Axle castle nuts do not have "fine" adjustments they are very coarse adjustments when compared to auto wheel bearing castle nuts..
You can read the instructions from Dexter..
HERE
