If in 2wd only the right wheel is pulling, I think that tells us something could be amiss with the left rear axle and drive gearing. I would definitely make sure I got the front tires corrected, but you might want to focus on the rear end first to see if whatever you might need there is expensive.
You should have a diff lock that you can engage to see if it works as designed. You might want to figure out if it truly locks up the rear diff. Find a surface where only the right rear is pulling (spinning without the left rear trying to turn), clutch the tractor, put your right heel on the lock and press it down, then release the clutch (if you take your foot off the lock it will disengage). If that doesn't make both rear wheels pull together, something is indeed wrong. And you may notice the noise changing, either getting better or worse.
I would think a dealer could make quick work with the diagnosis. They've probably heard a few of them make the same noise before.
Good luck with the diagnosis.
You should have a diff lock that you can engage to see if it works as designed. You might want to figure out if it truly locks up the rear diff. Find a surface where only the right rear is pulling (spinning without the left rear trying to turn), clutch the tractor, put your right heel on the lock and press it down, then release the clutch (if you take your foot off the lock it will disengage). If that doesn't make both rear wheels pull together, something is indeed wrong. And you may notice the noise changing, either getting better or worse.
I would think a dealer could make quick work with the diagnosis. They've probably heard a few of them make the same noise before.
Good luck with the diagnosis.