Growling at low speeds????

[Nathanialson 08]

Last saturday me and my friend were driving to go get food and my friend pointed out that my 08 Expy is making a weird growling sound when i hit the speeds of 30 mph or slower, i was told by my shop mechanic at work it could be that the brakes aren't fully disengaging or if thats not the problem it could be from under the hood, now i'm no mechanic past the point of being able to do doing oil changes, my own brakes and rotating tires, any ideas what could be going on?

 

[wwareham2008]

Does it only seem to kick in after you applied the brakes the first time, and only on one side? Because I also got this after adding my leveling kit. I have replaced brakes/rotors, rechecked everything I took apart and made sure I retorqued everything and it is still there. Some days it is worse then others.