Moan in the dark

[LDelco1]

Hello, We have a 1998 Chevy Tahoe. It has a noise coming from the rear end. It is NOT the typical whine associated to worn bearings. This noise is more like a Deep moan or rumble. It occurs at speeds above 60 mph, under load. Back the throttle off so it is just under a load condition, the noise goes away. I Have checked u joints, they are just fine. Have checked for any vibrations, and have not noticed any.
Anybody have any ideas??

 

[SunlitComet]

check your rear diffy fluid and condition of rear exhaust parts. could also stop getting your grove on in the cargo area.