On Wed, 1 Jun 2011 11:45:39 -0700 (PDT), Glenn Lyford
wrote:

this has a metal screw on dust cap. Does anyone know of a
vehicle that had a large diameter screw on dust cap?

Not off hand, anything with that style is likely to be ancient. As I
understand it, one style ofscrew on cap was used with bulk grease,
applied by hand, and then screwed down every so often to force more
grease into the bearing. Not saying that's what you have, but it's
beginning to sound like it.

The right way to fix this is to shell out the money to upgrade the
axles. There is no correct cheap way to fix this.
IF these are Reliable Axle boat trailer hubs, as I am starting to
suspect, the parts ARE available and reasonable - and they are high
quality hubs - and they may NOT be home-made axles.

These axles and hubs were fairly common on heavy duty twin axle boat
trailers several years back. (up to 3500 lb per axle)