2004 Chevy Monte Carlo rumbling sound follows vehicle speed

Hi, lately the sound is like an outboard motor that follows the vehicle speed, the trac off light was on this morning but it went out, the owners manual says that could be related to a brake issue involving the traction control system, I assume the abs system controls traction as well, the brakes still work fine but the noise has remained, it has 4 wheel disc if that helps. Thanks in advance for any ideas mick