Recently purchased a used 2010 Avenger. Noticed that when I get to about 60mph, I feel a slight vibration under the gas pedal and my seat. The vibration lasts for a couple seconds, then goes away for a couple seconds, then comes back and so on. The vibration goes away when I slow under 60. Not sure what is could be. Tires were balanced during inspection.

 

Get them re balanced and your alignment checked.

 

 

Next is to check cv axles, motor mounts, transmission mounts,transmission itself, wheel bearings, etc.