I assumed that you must be four speed. The front shaft which protrudes out of your transmission of your four speed is what I referred to as the pilot shaft. The pilot shaft "for a further example" has the spline which fits into the clutch center etc.

The frontal area of this shaft slims down to approx a half inch diamator and fits into a copper bushing which is located at the rear of the crankshafts rotating center. From the factory the crankshaft has this copper alloy bushing to compliment the pilot shaft. These copper bushings can and do wear out.!! They give off warnings such as you described. Continued driving when one of these has disentragrated from wear will harm your rotating assembly ie: rods mains etc. Gordo