Out of balance wont cause a whine. a bad tire can though.
Could be a wheel bearing, rear differential and so on. Take it to a shop so someone that knows what they are doing can look at. I am a tech, have been all my life. I can give a lit of the correct things to check but if your not a mechanic you'll have no idea if a part is good or bad unless it's very obvious (bulge in a tire, tire or part very loose and clunking).
I understand that everyone wants to come online to find an answer on a forum or YouTube to save money because so many claim that mechanics screw you over (some do, but most dont, and we have to pay for the shop, all the tools and equipment, cant do that on $10/hr though what places like dealers and big franchises charges is FREAKING INSANE). Plus 95% of DIY guys end up doing jobs 2 or 3 times because they miss something or make a mistake. Then on top of that the cheap parts dont last, not installed completely correctly so even good parts fail prematurely. Many shops will only charge a small fee to diagnose (and take it off the bill if you have them do the repair)
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