Aloha, my car shakes or rumbles,(not in the steering wheel) when driving between 40-45 mph. You can feel it in the floor by my feet and car seat. It feels like when you go over road strips or rumble strips. I’ve taken it to few mechanics and no one knows what it is. My tires have been balanced as they say, a couple times. It stopped for a few days after rebalancing but now it doing it again just not as bad. Any ideas. I would love to finally get an answer so I know what to fix.