NH TC30 - whirring/gear noise

[BrownTurtle]

2003 TC30 manual/550hrs (500hr service done)

Mostly runs good... Periodically needs to bleed hydraulics to get air out. However the other day, I was going down driveway and sounded like transmission gears were dry on oil. Just a mesh/whirring sound.

I put the tractor in 4x4 and it went away until I put it in High. Definitely higher speed dependant, but not at all higher speeds.

I checked the hydro fluid, and it's looks new.

Front axle looks good (full/clear).

Any other ideas? Clutch?

Thanks.

 

[nyone]

Front hub oil?