whinning in brand new ranger

i just bought a 2007 ranger XLT supercab with a 3.0L V6 auto tranny. i also have to 3.73 gears and tow package.
from the first day i bought it ive heard a whinning noise as i start out from a dead stop. it raises in tone from 0 to about 15mph then it stops. i can also hear it when im coming to a stop. this is not a sound i would think a brand new truck should make. it also feels like it drags a bit when i let off the gas pedal at any speed. with the first tank im getting 17.89 mpg. any info before i take it back to the dealer would be great.
thanks everyone and have a great one.

i have an 04 ranger with a 4.0 v6 and it has 4:10 gears in it with an automatic and towing package. my ranger does the same thing. its normal. you will also hear a loud noise in the dash board when you turn on your air or heat and its also normal. don't worry with that noise. its just the tranny getting out of a low fist gear.