Not entirely sure this is an issue in the rear axle, but Id almost bet money on it. Basically, as I drive, this rubbing noise is coming from under the suburban as I drive. The tone does NOT change with the trans, so I believe it the rear end is bad. Im looking for advice, confirmation, guidance...anything I can get. I made a quick video of it. The suburban is on jackstands. My wife "accelerated" and braked a few times so that you could hear the sound it makes. I figured it was easier than trying to be over descriptive and possibly misleading.

96 GMC Sub
C1500
5.7 Vortec

 

First thing I'd do is have someone step on the Brakes/engage emergency brake, and check the rotational slack in the drive shaft.
That shouldn't be over 4-5°, or 1/2" if you measure the circumferential movement.

Next, maybe pull the plate, and check the ring and pinion bearings and clearances.
Also, there are heavier oils available, if the above is excessive, and you just want to do a temporary "help" fix.

PS:
I'm not really sure just what that sound is, but, thanks for gong to the trouble of recording it.

 

Sounds to me like planet gears. Remove the plate, you will know if it is them I had to replace on my 2k sub.

 

pull the cover/check fluid and you'll have your answer, pinion bearing may be shot

 

Im kind of a noob with this. If the rear cover plate is off, how deep should the fluid level be? To the bottom of the cover plate opening?

 

On most Differentials, the Filler Hole and the "Proper Level" checkpoint, are the same.

One may (when dry) add a specific amount to the Differential, or, add fluid/grease till it just runs back out of the Filler Hole. You may note, that the hole is positioned at/just below the lower line of the Axle Housings.

 

Put your pinky in the fill hole, point it down, if you can feel it, it's fine. Thats with the cover on

 

i have a 95 suburban and it was making a similar noise,then it turned to clunking,turns out it was the ring and pinion.when i pulled the cover 1 tooth was broken off of the pinion and 2 teeth were broken from the ring gear.