2003 GMC Envoy Noises

Noises problem
2003 GMC Envoy 6 cyl Four Wheel Drive Automatic

What you cause a humming noise that is coming from
the Rear End or somewhere in that area.

It does it when I step on the gas.?

It is not loud and the car runs Ok...it just has this
noticeable noise.?

Can't say for sure where it is going from?

Thanks