I have them on my '06 trailer. At first I thought I had problem because the oil turned milky, like water had mixed in. I found a tech sheet about them which has a note that says it is normal for the oil to change color during use.
Lately, I have noticed that one of the hubs is leaking oil on my gagare floor. I had to remove the tire/wheel and add oil. While adding oil, I noticed that the hub moves a little bit. Again, I checked the tech sheet. It mentions that if the axle has steel wear sleeves, a high temperature sealant must be used on the axle where the hub seats or it will leak.
I emailed my dealer and they could not answer my questions about the steel wear sleeves, so I emailed Tracker Customer Service. I received a response from them today;
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