question Ursus C385 - Back end noise

Hi
I'm new to forum it seams to be the place to go for zetor info.
Anyway I have a ursus c385 with a bank end noise it drives ok but when in top gear when I let of the throttle there's an ofal rough noise from the gearbox/ backend like gears greating or not meshing also when I took up the backend dipstick there's lumps wore out of it. So I have a problem and help would be great
Regards Richie

Is the noise in all gears or only in top gear ? Or does the noise increase when drive speed increases ?

It's not so bad in 1st and 2nd it's mostly in top gear if I'm coasting down hill in top gear and the tractor is pushing itself on that's when it's noisest its a very rough grating noise not a whine noise

Does the frequency of the noise change with engine speed or with drive speed ?

Most likely a pinion bearing if the noise increases with drive speed.

It seams it's drive speed it's not to noticeable in lower gears. I'm guessing it's a big job to do the pinion bearing is there much striping down to get to it
Regards Richie