I have a 2002 gmc sierra 2 wheel drive and when I take off initially and when I turn left I hear a grinding/grumling noise.

Loose or damaged Wheel-Bearing causing other parts to rub together, like the brake components or your wheels are too big or shocks weak, or exhaust hanging and are rubbing against something.
Perhaps oil is leaking from your rear axle housing dut to bad seals (check inner of wheels) and around axle housing - remove plug and check that your finger can reach in and touch it. Could be a sign of rear end failure or simply the backing plates on the brakes behind the rotors and the drums (steel disk) sometimes rust on the drums can grind against the backing plates if they are weak or warped (clean this area).