Gear Box Whining

[Holdenfarm]

I just replaced the throw out bearing in my major. I checked out the gear box while it was apart, the best I could. Everything seems tight. However after putting it back together it has a whining sound coming from the gerar box. It sounds worse when in high range, however I have noticed when I take open the filler plug on the left of the gear box I can hear a rattling sound now from in the gear box. I have read through some posts and noticed the upper rear bearing seems to be an common issue. Is there a way of checking it without splitting the tractor? I have access to another gear box and rear end. I am debating rebuilding the extra one and just switching them when I am done.
My major issue is hay season is less than 4 weeks away, and this is my mowing and raking machine.
Any help please, where to start looking, maybe starting with easiest bearings to check.

[AdrianNPMajor]

Hi Rob
Drain gearbox and remove the selector cover on the left side (see first photo). You'll be able to see the upper bearing. As you can see, mine was u/s.
I noticed something was wrong when I had the tractor up on axle stands and took her through the gears. Sounded very rattly indeed in top gear high box (sixth in other words! ).
Best
Adrian

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