45" flathead has roaring/whirling noise in transmission when idling in neutral

[Buster]

1956 Harley Servicar. Has roaring/whirling noise in transmission when running in neutral. Same noise with clutch engaged or disengaged. I can put in gear and noise immediately goes away and transmission sounds good. What would be cause of noise in neutral only? Thanks!

[Rubone]

Check your oil level. Also can be caused by a badly worn 2nd gear or low gear bushing. In Neutral there is no load on those gears and they are not spinning at the same speed as the countershaft they are on.