JD 1010 Whining in the gearbox

[drafter]

I have just bought a 1961 JD 1010 gas tractor. It is in very good using shape. There is a whin in the gear box that stop when yo push the clutch in. Should I be concerned about the noise or just run it until something breaks. He had said that when he got the tractor that ther was some water in the trans from being left outside. He changed the oil and he said the noise is better. Would something like Slick50 help the situattion.