for the last few days I been hearing a humming sound that comes and goes.It seems to be coming from the passenger side rear wheel.I only hear it when im going 30 to 40 mph then when i go faster it stops or slower than 30 i dont hear it.But then sometimes it doesnt do it at all very odd.What could be making a humming sound from the rear like that ,that comes and goes anyone?

 

Check fluid level in the rear diff.

If that's ok, jack up the rear end, and spin the tires by hand. See if anything feels off. Could be an axle bearing going out.

 

Thanks for the info if the rear diff is low what fluid should I use?

 

80W90 gear lube, need to know if you have limited slip rear, as if you do, you need the friction modifier as well. (Or, 75Wsomethingorother synthetic, if you tow/haul often)