Wheel noise or rearend going out?

Hello everyone, im looking at a 99 z28 auto, and theres a sound ( sounds like its from the rearend. And its the rearend growl. But it only can be heard at all at 60 mph. I had a rear go out and the growl was heard even at slow speeds. Now they had the rearend rebuilt 2 months ago ( with reciept) and they did put on the cheapest tires they could find ( 4 installed for 250, and they are new). there saying that the noise came with the new tires. Seem like very honest people, just getting your guys opinons. thanks

Pretty hard to say with this info. You could try jacking the rear up and putting stands under the axles. Start the car and run it up to an indicated 60mph. See if the sould is still there. Or of course change the tires.