While plowing yesterday (and again this evening), I heard a "squeek" sound once in a while.
When I pulled back into the barn, I jacked up the front end and spun each front wheel to confirm my thought and yep, I was right! Front wheel bearings!
I removed each wheel and 1 bearing in each wheel was shot, but not the axle or wheel...lucky me.
All the bearings, races and seals still have TIMKEN and NATIONAL numbers on them so I plan on locating repair parts tomorrow!
I will try to remember to get photos of the problem and repair tomorrow.