loud takeoff

I may sound stupid since I have never owned a truck new enough to have a vortec engine. What would make the engine sound so loud during take off to around 20 MPH? My 72 and 93 blazer doesn't do this but my wife's 99 suburban and friends 98 blazer does. Both have vortec engines.

If the sound is present when the engine is cold,it is most likely the thematic hub is engaged and the fan is pulling air through the rad.
chuck's