leaking seals trailer axle

I run 100% Lucas on my axle's. They never leak.

 

Either the seal flange shoulder is worn or for some reason the wheel is moving too much on the spindle. With at 17-18 year old trailer chances are there is some spindle wear and the rust line has moved too far inward for the seal shoulder flange area. Going to grease is fine, nothing wrong with that. When I put a seal in I like to use some #2 sealant on axle flange shoulder and some on the OD of the seal where it seals into the hub, if you are using CR brand.
How bad are the leaks. Some minor seeping is normal. Also, try replacing the rubber plugs in the hub cap. Sometimes they get plugged and do not allow the hub cavity to breath and when the bearings warm up and the air expands inside and the oil gets pushed out the seal.

 

Where specifically is the leak? I've had the oiler hub caps get dry rotted and leak and need to be replaced too.

 

I inherited a problem child like that and found that the previous installer had replaced all the bearings and races, but he was supplied with incorrect tapered roller bearings for the application. The bearings had larger inside diameter and so they didn't fit the spindle properly allowing much movement of the spindle in the bearings. Check your bearings being used for proper application of hub and axle. You can do this through your hub seal catalog. We also exclusively use stemco seals with grit guard wear rings. This eliminates a lot of problems.

 

Stemco 2 piece may also help, they still use leather for the seal surface. It swells and is much more forgiving with troublesome spindles!