OK, here's the story. I was driving home from a 90-100 mile trip when the three speed in my '53 popped out of gear. This has never happened before. About 20 miles after that happened I noticed a slight vibration at cruising speed. It has gotten worse in the past week. It goes away if I accelerate, decelerate, or push in the clutch. Sometimes if it's bad I can disengage and re-engage the clutch at speed and the vibration gets better, sometimes goes away, temporarily. I checked the gear oil in the transmission, it was about an inch below the fill plug. Gear oil in the rear end is full. The U-joint looks as good as new. Is my tranny failing? What should I be looking for?
