I've been noticing what sounds like a mud terrain hum when driving at low speeds. I read around on this forum about wheel bearings going bad.
I just changed the diff fluid last fall and added the limited slip fluid with the gear oil only to find out I don't have limited slip.
I raised the rear axle off the ground and spun both tires. I get the same noise from both sides.
Could this be the bearings going bad? Or could the limited slip fluid be causing the gears to be noisey?

 

Does the noise only happen at low speeds? If it is a constant noise, i would suspect the bearings.

 

The friction modifier should have no adverse effect on an open diff

 

I didn't think the friction modifier would cause noise but I wasn't sure. Yes it is a constant noise. I read about changing the bearings doesn't look like its to much of a job.

 

I pulled the drum off and moved the axle up and down. There wasn't any play in either axle. If the outer bearing are going bad while they get loose like the front bearings?
I just don't want to tear into this thinking it's one thing and have it be something else.
Anothern question I have how do I find out if it the inner bearing or the outer with out taking it to a shop