2005 dodge grand caravan harmonic noise

I have a 2005 dodge grand caravan SXT with 50k miles on it. There is a vibration/rattle that I notice at around 1200 to 1300 rpms. it is most notable under light pressure on the gas pedal when also going around 38 mph or 25 mph (seems to occur through all the gears but the noise is much more noticeable in the higher gears). Dealer thought it was alternator and replaced, but no effect. Anyone have thoughts on what to check next? Thanks,


Not sure if this is the same thing on my 2006, but I have a low growling noise in the rear when slowing accelerating between 40-50mph. Does not do it if I speed through 40-50mph. Dodge people don’t know what it is or can fix it. It’s been there nearly since I purchased it two years ago, and has not gotten worse. If I but a heavy load in the back behind the seat it is diminished.