There’s usually a funny noise long before any catastrophic failure, so I think it’s the bearings or the gears, but concrete information is hard to find.
I actually had my motor replaced due to this noise. It was a high pitched whining, kind of like a jet engine spooling up. Not real loud, most noticeable in a parking garage with the roof open, and I wasn’t even sure if it was abnormal, but I took it in and they replaced it. It’s easy to swap out, so they just put in a new one and then fix the old one at their convenience and give it to the next victim.
Incidentally, I had another weird noise sometime later which was a distinct clunking sound when accelerating from a stop. That turned out to be a bolt that wasn’t tightened properly. Oops!
