Trailer Issues

Grease or hub oil?
New bearings fitted?
Are you shure the bearings aren't to tight or to loose?
Which brakes?
Disk or drum?
Which tires?
Pressures checked?
Same brand off tires on both sides?
Did you use a temperature gun?
Is the airflow the same on both sides?
Toolbox on either side?

 

If it has trailer brakes, I would check that side isn't dragging causing the grease to overheat compromising the bearings. Or the opposite trailer makes aren't working and that side is getting overheated from doing to much work

 

Airflow.............is there anything different between the 2 sides that could influence the cooling?

Get a temperature gun.
measure tires ,drums and hub caps .
Do it empty and loaded.
Loaded i would do it after 5,15 and 30 min driving.
It will build a picture off where the heat is coming from.

 

You need to check the preload on the bearings. Are you packing the bearings before install? Are you filling the hub cavity with grease? Sounds to me like the bearings are to tight and they aren't packed enough. Also, what are you using for grease? Is it a quality GC-LB grease? Some greases are thinner than others and will start to break down with heat and not give you good wear properties. Try repacking the bearings with a thicker grease, make sure your torque on the axles is correct. What axles are in it? Dexter? Is it a dual wheel or single wheel trailer? What bearings are you using? Name brand? Chinese imports? Are you changing the cone and the bearing or just the bearing?

 

Not sure how you did it, but this is how I was taught. Disassemble the hub, remove both inner & outer bearings, visually check for wear. If they look good, run them through the parts washer, clean 'em good and blow then blow them clean with compressed air. Strongly resist the temptation to spin them at 6,000 rpms, don't do it. Inspect them again, if good, pack them by hand by putting a big gob of good quality high temp grease in the palm of your hand. With the other hand holding the bearing force the grease up through the rollers until it comes out the top, rotate until each bearing is fully packed. Clean off the spindle and remove the old seal from the hub, replace your inner bearing and install new oil seal. Liberally apply grease to the spindle. Re-assemble, tighten spindle nut until seated and then back it off 1/2 a turn. Spin the wheel some more, both ways, re-seat spindle nut again and then again back it off 1/2 turn, check for excessive play or binding, and if good replace cotter pin and cap.

What cap are your axles, 3500, 7000? Round bales or square, what's your weight vs trailer capacity?

 

This solely sounds like an installation error. Without being able to answer most of the important questions it's hard to go further. How can you say they use a good grease? I'm going with the bearings are to tight. If you continue then you could damage the spindle. Put the trailer in the air on your own with a jack and spin the wheel. Being the bearings are now worn in, it should spin with little resistance. If it takes force, your to tight, remove the caps and back the spindle nuts off an 1/8th of a turn at a time, no more. You don't want them to loose, then grab the tire outside edges and check for excessive wheel play and reinstall the cotter pin and cap. And even at this point, if they are to tight, it's possible that the bearings have lost some of their temper and will need replaced again.l, but this will help narrow the problem. I'd assume that it won't matter, loaded or empty but the heat will continue to rise. There will be a temperature difference on loaded and empty, but I bet it will still be hot when empty..