I was wondering if it could be that bearing. I am hoping I can find a quality replacement (not made in China) for it, and start there. The rubber membrane that surrounds it, is kind of dry-rotted anyway, so it wouldn't hurt to replace it.

1964 C-30 http://s1179.photobucket.com/albums/x383/autoart3/64%20one%20ton%20dually%20flatbed/