2002 Chevy Silverado honking noise and grinding/squealing

first off i would like to thank you in advance for your response. Question 1: after coming to a stop and then accelerating a honking noise comes from the rear of my truck. i was just wondering what it is. since yesterday i also heard 2 silverados and 1 sierra do the same thing. question 2: while going under 5 mph there is a grind/squel noise coming from the rear also. i took it to a shop and i told them either my rotors are shot or the axle bearings are going. the inspected the rotors and they were bad so we replaced them. 1 week later the noise starts again. is there something else this could be. dont want to fix something again that is not the problem. Thank you.