98 Gand Marquis grinding in the steering.

I have a 98 Grand Marquis with 154,000 miles on it. I replaced the upper and lower ball joints, and tie rods two years ago. Also replaced the pitnam arm at one point. When I back out of my drive way and turn the wheel (the car is more or less stationary) , I get a slight grinding noise. Is there another suspension part that I should be looking to replace? Thanks M