The machine is due for a full service and I'm planning on doing the service this spring and making a video about it. Rolling back to my initial thoughts, it could be a filter screwing up but more likely it is either the HST pump shims (unlikely) or the internal solenoid that controls the HST pump's volume (more likely).
I've got another new dealer who hired a proper tech and he and I discussed the issue after the tech determined my machine is not in the serial number range for the recall. The new dealer is part of a dealership chain (everybody has been consolidating) and the northern shop doesn't have the equipment to split tractors. As a result, the tech I spoke to has not directly worked on the HST transmissions, but the southern shop has, and so he shared what the southern shop had learned.
Anyway, since I'm not made out of money, I have no recourse other than to let it buck, or split the tractor myself in the summer using my payloader to lift the cab up and off and I'm inclined to let it buck.
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