Could be something with the speedometer drive inside the transmission and the rear bearing support. It has been a few years since I worked on that 3 speed, but I recall the speedometer drive gear consisted of a worm gear which was pressed onto the main shaft. The worm gear turns a toothed gear (which is your speedometer drive mechanism). And to remove that speedometer drive gear assembly I think (emphasize the word "think") you have to remove the rear bearing support. Wish I had taken pictures of it...but digital pictures were still 20+ years away at that time. You mentioned replacing the Oakie bushing. I'm wondering if those are connected.
