Fly wheel is the on for the 4.8. I did grease the pilot bearing. It is for sure gear whine. It only will do it in 1,2,3ird... 4th and 5th its fine. its farly loud. In neutral it makes a slight noise when my foot is off the clutch. When i put the clutch in it goes away

 

With 186K miles, I'd say it's time to replace it. Might seem odd, but mechanical devices stand over time as they are, then replaced, removed exchanged, don't like it. New overhauled engine, I'd do the same with the tranny my opinion. You can use plasti guage to check the gear mesh, however I don't know what to tell you it should be, also if it is out of limits it still dictates a new tranny, again in my opinion.