Okay guys, the filter cavitation problem seems to be mostly fixed. I say 'mostly' because it still went into making that noise briefly as I was test driving it. But it was fine at higher RPMs whereas it made noise anywhere above 1500 before. I reckon give it some time before passing final judgment.
The filter was $28 and came with a filter cover gasket. The AMBRA 134G was $79 for a 5 gallon bucket. It was noticeably thinner than 'universal' fluids I've seen by far. New Holland must be using it in everything now because the store shelves were well stocked with it, white buckets with orange lids everywhere.
Anyway I'm somewhat relieved, but the SOS transmission still makes a lot of noise in my opinion. More than what this old retired mechanic considers 'normal'. Most of the whining is coming from the front of the tranny, right below the steering column. It whines whether the tractor is moving or stationary, in gear or park. The noise level remains constant no matter what the RPMs.
As I said before, all the gears pull fine and it shifts firmly, even abruptly when not using the 'inching' pedal. No gunk or particles in the old fluid.
I guess I'll just have to get used to it... :confused3:
Thanks to all for your invaluable knowledge and much appreciated advice! :drink: