My rear end seems to be making a couple different noises.

When I'm accelerating from about 20 mph or more, in any gear, it'll make a "woowoowoo" humming sound similar to tire noise. But then as soon as I let off the gas and let it coast, the humming disappears and a whine takes it's place.

Why would it make two different noises like that? It doesn't whine at all when driving, only when slowing down. And the hum can only be heard while driving and not while coasting....I don't get it.

 

If you've had new gears installed receintly, they may not have been shimmed correctly. If not, you may want to check your rearend fluid.