B7800 makes a winning noise
2007
B7800 4x4 makes a RRRRRRRR noise some times when moving fast , [to me sounds like a relief valve ] but I have little experience , I did change the hydro oil and filters ,no metal parts. dealer can,t look at it for a month . [I like my dealer there just busy]
Have you had this tractor since it was new? Is this a newly developed sound? My
B7800 makes a similar sound in certain circumstances. - a whine from transmission. Using the Kubota super deluxe (I forget what it is really called) hydraulic oil made it diminish significantly.
My
B2910 (same as 7800 with premium features) has a whine in high gear at near top speed. If this is the type of noise you are hearing. It is normal because of the straight cut gears.