Engine Vibration

[davidb3265]

My 2011 Chrysler with the 3.6 engine and six speed transmission has developed a vibration. It occurs at about 1750 rpm in all forward gears but is most noticeable in high gear on the highway. The engine has to be pulling for it to occur. Any time the car is going even slightly up hill it can be felt. I have checked all the usual things and replaced the spark plugs thinking that it might be a misfire. It is always the same engine rpm and the car has no other problems and no engine codes. It has approximately100000 miles on it. Any ideas?
David B