Just noticed for the past couple of days when I turn the steering wheel at low speeds, like parking lot, driveway or slowly at a dead stop, I hear this low rumble noise...maybe a bit of a groan. I can only hear it INSIDE the car? It doesn't matter which direction I turn the wheel. If someone steers and I'm outside the car with hood open, or standing next to wheels I CAN'T hear it. It kind of sounds to be honest like it's under dash or behind the dash. Any ideas/suggestions? The steering feels fine and fluid is full and fairly clean looking. Thanks!

Even stranger, this noise does not occur until after driving. When started from cold, I can turn the wheel without sound. By the time I get back to my driveway...I can hear it. 1985 300SD.