[LMP]

Hard to tell. Standard check list would be tires, alignment, hub assembly....but you've taken care of the last, at least...
Humming pitch is important...hub assembly frequency is rather mid range, say like 300Hz at 60mph, and changes with changes in direction, increases when turning on one side, decreases on the other...so these details are important.
Low pitch ..like 80-100 Hz rumble, can be cv joints....or transmission/differential output bearing....
Both of the above are speed sensitive.
High pitch buzz seemingly coming from transmission is frequent, inocuous, and seems related to pressure regulator, changes in intensity if one connects and disconnects vacuum from vac operated transmission modulator (not your model I think) and this one is rpm related....
...so....please add any of your findings to the list..it can help others.
Happy new year..