I just bought a 2017 F-150 5.0 V8 with 70k miles on it. Got a vibration on the floor of the driver's seat, also on the gas pedal. It's nothing crazy but most noticeable when: going 40 - 70mph, accelerating, when on an incline, and is totally random at times but was the worst on my last test drive when I was in fifth gear @ 2,000rpm. The rotors are abnormally hot as well, even after driving for only a few miles. Just changed the brakes and calipers and the tires are in great shape.

 

Welcome.
Bring it back to the seller, have them address the issue..
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Welcome.

 

Welcome!